When you create a repl, it can either be public or private.
Private repls can only be accessed by people in your team that are members, and by guests who are directly invited to these repls. You can make a repl private when you initially create it.
Public repls can be accessed by anyone who has the repl URL, allowing them to fork and copy everything on the repl. This is a great way to share code with people outside of the team. Only team members can edit the original repl.
You can toggle between "private" and "public" from inside a repl, as many times as you want, by clicking on the repl name in the top left of your screen.
You can fork any repl, private or public, by clicking on the same repl name and then clicking on the three-dot menu, and selecting "Fork".