What are the 4 types of essay and how do I know which one I'm supposed to write?

My professor assigned an essay but didn't specify what TYPE of essay. Just said "write about this topic." And now I'm spiraling because aren't there like... different kinds? And if I pick the wrong one, will I fail?

I Googled it and now I'm more confused. Some sites say 4 types, some say 7, some say 15. But the main ones seem to be: narrative (telling a story), descriptive (painting a picture), expository (explaining something), and persuasive (arguing a point).

So if my topic is "the impact of social media on teenagers" — which one is that? Expository? Persuasive? Both? Neither?

I asked my roommate and she said "just pick one and go with it." But what if I pick wrong? What if my professor was expecting persuasive and I write expository and she takes points off?

My friend said to look at the prompt for clue words. "Explain" means expository. "Argue" means persuasive. "Describe" means descriptive. "Tell a story" means narrative. But my prompt just says "discuss." What does "discuss" mean??

Has anyone else been confused by this? How do you figure out what type of essay your professor wants when they don't tell you?

The 4 types are a useful framework but in reality most college essays are hybrids. For "discuss," what I'm usually looking for is:

1. Clear thesis/position
2. Evidence from sources
3. Acknowledgment of complexity/other views
4. Analysis, not just summary

That's closer to persuasive but with expository elements. So for social media, you might argue something specific but also explain different perspectives fairly.

Your clue words method is good but "discuss" is the wildcard. When in doubt, make an argument supported by evidence. That's safe 90% of the time.