What do people on the loo?

It seems you're asking about what people do on the toilet, or the loo as it's called in some places.

It's a bit of a sensitive topic, but here's a polite answer:

People use the toilet for their bodily functions, specifically going to the bathroom (urinating or defecating).

It's a natural and necessary part of life, and there's no need to be embarrassed about it!