Reply To: Apply style to every other/every third paragraph?

InDesign's GREP is different in the sense that it can also deal with typical InDesign attributes, and that's not something you can find anywhere else! (*)

But in general, the typical GREP commands are the same as anywhere else. There are a couple of 'dialects' of GREP, so not everything you find on https://www.regular-expressions.info/, for example, will work. I have a list of supported 'standard' functions at https://www.jongware.com/idgrephelp.html.

(*) It's also mentioned in the online help, of course. But you hardly can learn to use GREP from there, as it's just a list of commands.