You can create a community with the same name as an existing community. In that case, several communities with the same names will be displayed on the community list.
The behavior described applies for a restricted community. You cannot have multiple open or moderated communities with the same name. If you try to reuse an existing community name for an open or moderated community, the message "A community of that name already exists" appears. However, you can have multiple restricted communities with the same name.
If you want to avoid using an existing community name when creating a restricted community, search or check the community list first to avoid any duplication.