The first step in getting started with Matrix is deciding which homeserver to join. Your homeserver is the url at the end of your Matrix username, everything after the : in @example:matrix.org. When you initially register for your Matrix account, you'll need to choose a homeserver where your account will be based. Your homeserver doesn't affect who you can talk to - any homeserver can connect to any other homeserver.

It doesn't really matter too much. The foundation that develops the Matrix protocol operates two official homeservers, matrix.org and vector.im, but there's dozens of different servers that allow public registration, some of which are listed here. Make sure to choose one that's up-to-date, preferably with a well-defined privacy policy.

None of the servers at the URL linked above are endorsed by the Matrix Foundation or Veilfire.
Different homeservers have different rules about what conduct and content are or are not allowed on their network. 
Make sure you check the server's rules and/or code of conduct before joining.

If you'd like an invite to register on the :veilfire.net homeserver, you may request one by contacting us. Our server is small and has limited capacity, so registration is generally open to co-op members and friends. If you already have an invite key, you may register here.