It can take a little time to settle in to a new community as they often have different expectations and guidance around what is and isn’t acceptable for their particular site. The best thing to do is to take the time to read through any forum guidelines and welcome topics they might have which should explain more.
Using the Search is also quite widely useful, as a lot of basic questions will have been asked and answered before.
There are some topics on Meta that describe the defaults, though these are generally more useful to admins than end users if you’re not looking specifically for the guidelines for here.