Lecture slides with no explanation? How to actually understand them

Lecture slides with no explanation aren't unfinished by accident. They're built for your professor to talk over. That's why, when you open them alone at home, nothing makes sense: what you're looking at isn't the lecture notes, it's the script the lecture was given from.

The good news is that the script says more than it seems. The titles, the order, the words your professor picked and the slides around each one give you the skeleton of the topic. Your job is to rebuild what was said between the bullet points, and there's a method for that which works even if you missed that lecture.

I'm a final-year computer engineering student, and half my courses were like this: forty-slide decks with a title and three or four words per slide. Here's how I study them, using a real example from my operating systems course.

Why lecture slides have so little text

A lecture deck does a different job from a textbook. It's designed so you look at the professor, not the screen: if it had full paragraphs, you'd read instead of listening. Plenty of professors build them sparse on purpose, and for the lecture itself that's fine.

The trouble starts later, when that same deck is all you've got to study from. Three things get lost along the way:

• The why. The slide says what something is; the why was said out loud.
• The example. It's almost never written down, and it's exactly what makes a concept click.
• The connection. How this slide relates to the previous one and to last week's topic.

Knowing what's missing already points you somewhere: the answer isn't rereading the same slide, it's going and finding those three things.

Read the outline before the words

Before trying to understand any single slide, flip through the whole deck in one go without stopping. Ten minutes is enough.

Look for:

1. The titles, in order. Together they're the table of contents of the lecture. Write them as a list and you'll see how your professor structured the topic.
2. What repeats. A term that shows up on five slides is central, even if none of them explains it.
3. What's emphasized. Bold, color, boxes, a slide with a single sentence in big type. That's where your professor slowed down.
4. Section breaks. A slide with just a title usually means a new part is starting.

My example: in operating systems there was a slide titled "Deadlock" with four bullets: "Mutual exclusion", "Hold and wait", "No preemption" and "Circular wait". That was it. Looking at the outline, I saw that the slide before was about processes sharing resources, and the next three were titled "Prevention", "Avoidance" and "Detection". That already told me something important: those four bullets were the foundation for everything after them.

Turn every bullet into a question

You can't study a two-word bullet, but you can study a question. For each one, write at least two:

• What does it mean?
• Why is it here?
• What would happen without it?

For the deadlock slide, that gave me: "What is mutual exclusion?", "Why does deadlock need it?", "What happens if I remove just one of the four conditions?". That last one made everything fall into place: if breaking any one condition is enough to prevent deadlock, then all four have to hold at once, and the "Prevention" slide is literally a list of ways to break each one.

The questions you can't answer become your to-do list. Don't skip them: they're exactly what you're going to go look for.

Look for the gaps in the right places

With a list of questions in hand, searching is much faster than reading a whole chapter blind. This is the order I go in:

1. Notes from someone who was there. Even messy ones have the example your professor gave and what they said would be on the exam. If you missed the class, I wrote a full guide on how to catch up on a missed lecture.
2. The course textbook. Not the whole book: look up the terms from your questions in the index and read only those pages. Lecture decks often follow a specific chapter.
3. The lecture recording, if there is one. With your questions ready, you can skip straight to the part you need instead of rewatching everything.
4. An AI chatbot, with context. It works well if you paste in the slide and the ones around it, say which course it's for and ask one of your specific questions. It works badly if you just say "explain this" with one slide on its own: it'll fill the gaps with the most generic answer possible.

With those last two, double-check. If the explanation disagrees with your professor, your professor wins, since they're the one writing the exam.

Let someone explain it, slide by slide

What I really needed in those courses was the one thing I didn't have: someone walking me through each slide the way it was presented in the lecture. That's why I built Filmina, a web app that explains your lecture slides out loud, slide by slide, with a frame that points to the part of the page it's talking about. On a slide with four bullets it doesn't stop at reading them: it tells you what each one means and how it connects to the slide before. And if you get stuck on a term, you can ask about that slide or the whole lecture right there, and it shows which slides each answer comes from.

Whether it's an app, a classmate or the textbook, the idea is the same: don't sit staring at three words hoping they'll explain themselves.

Write the slide your professor didn't

The last step is what makes everything else stick. Under each slide, or in your notes, write in your own words what you found: a sentence or two per bullet, one example and how it links to what comes next.

For deadlock, my version went roughly like this: "Deadlock is when a group of processes are all waiting on each other and none can move forward. All four conditions have to hold at the same time, which is why breaking any one of them prevents it. Example: two processes that both need the printer and the disk, each grabbed one and is waiting for the other."

Three things that help me:

• Write without looking at your sources. Read first, then close everything and write. If you can't, you don't understand it yet.
• Use your own example, not the textbook's. One you come up with sticks much better.
• Don't copy whole paragraphs. The goal isn't to turn the slide into a book, just to add enough that it still makes sense a month from now.

You end up with the deck you wish you'd been given, and studying from it for the exam is so much easier. If you want the full process for an entire course, I covered it in how to study from lecture slides.

Frequently asked questions

How do you study from lecture slides that have almost no text?

Flip through the whole deck first to understand how the topic is structured, turn each bullet into questions and find the answers in classmates' notes, the textbook or the recording. Then write what's missing in your own words under each slide.

Why can't I understand my professor's slides?

Because they're designed to support what your professor says in the lecture, not to be read on their own. They leave out the why, the examples and the connections between topics, which is what was said out loud.

Can I use ChatGPT to understand a lecture slide?

Yes, if you give it context: the slide, the ones around it and the course, plus a specific question. Always check the answer against the textbook or what your professor taught, because it can fill gaps with something generic or wrong.

Should I go to lectures if the professor posts the slides?

Yes, especially when the slides are sparse: what you lose by skipping is exactly what isn't written down. If you can't make it, get notes from someone who was there that same week.