Niche

Your niche is the subject you post about and, more importantly, the audience that subject attracts.

Why brands care about it more than size

Because a niche audience is a buying audience. A creator with 8,000 people who all care about one specific thing is often worth more to the right brand than someone with 80,000 general followers, and priced per thousand views the gap can be several times over.

Niche is the single biggest factor in what you can charge, ahead of follower count and ahead of engagement rate.

Choosing one without trapping yourself

The common fear is boredom, and it is reasonable. The way out is that a niche is a subject, not a format. "Personal finance for people in their twenties" allows enormous variety in how you cover it.

What does not work is switching subject repeatedly. Each switch resets what the platform knows about who to show you to, and the audience you built for the last thing does not follow you into the next one.

Signs yours is working

The comments are specific. People ask you questions rather than complimenting you generally, and brands in one industry start arriving without you pitching.