These are called a gTLD or Generic Top Level Domain.
There can be a variety of gTLDs but most that you will use will either be country specific (all two letter gTLDs are reserved for countries) or newer topic focused gTLDs (.xyz, .plubming, .store, etc).
If you can register the domain you want, it doesn't matter what gTLD you use, but each gTLD is operated by a different entity and each may have its own rules for who can buy/use domains under their gTLD. Some are very permissive and you just need to pay (.com, .io, .ly), others are more restrictive and may be hard to obtain. For example, Ireland (.ie) strictly requires that the content on .ie sites be relevant for people in Ireland. Accordingly, a US corporation cannot generally obtain a .ie domain for use as a BSD.