Why are Unity events so special?

Hi, I was looking into a problem in my code and I came across a thread that talked about events. Then I looked up events, watched a few videos, read some forums, and I'm baffled about what's so special about them... What's the difference in between declaring an event and initializing a public variable, putting an if statement in update, and calling a function there? I've just heard a lot of people like them.

The problem that I've been dealing with, and wondering if it would be easier to fix with events, is as follows: I have a bunch of enemies in my scene that don't do anything until a certain amount of enemies have already been killed. I wanted to make them inactive until they need to be present to cut down on checking for collisions, rendering, etc.

Thanks in advance!