First of all, I am not sure if I can ask this question here, and, if not, I appreciate that you indicate me the best website to ask this question.
I have been reading about ASs (Autonomous Systems), ISPs (Internet Services Providers) and RIRs (Regional Internet Registries).
For example, I understood that there's a big entity at the top of the RIRs that actually is more powerful than RIRs, we are talking about IANA. This IANA is for example responsible for allocating IP addresses or to give ranges of addresses to RIRs (as far as I have understood).
ISPs are for example the telephone companies that allow you to connect to the internet through their service. They usually give you a modem (and a router), and, when you want to access some website (for example), the request passes through their servers.
ASs, as far as I have understood, can be many ISPs put together or just one. An AS exists because the entities that take part of that AS share the same policies, for example the same routing protocols (e.g., OSPF).
I am not sure if the description I gave are correct, but I am pretty sure they are quite incomplete. Since I have not found nothing really satisfying that describes the difference between autonomous systems, ISPs and RIRs, I decided to ask here a question with the hope of receiving an exhaustive description of what they are and what's the difference between them.