What does Global mean in ranks in Minecraft (Pe)?

I've created ranks on my (LEET) server, and thought so far that's all right, but now I've seen tutorials for ranks that I have not made "global" at any rank, I had no idea about it (I still have can't anyone explain what makes this "global" in the ranks?

"global" means on all servers.

If you have multiple servers then you can just give permissions that should only go on one server.