Explain Spaced Tags

Can someone please explain spaced tags to me? Idk lol.

I know this response is a bit late but on xbox if the gamertag "O G" is taken then so is "OG".
So if you're looking up a gamertag using account.xbox.com/en-US/Profile?gamerTag=OG (It appears to not exist)
but if you got to https://account.xbox.com/en-US/Profile?gamerTag=O G it does.

If someone has the GT 'Up rise' you won't be able to get the following...

Uprise
U prise
U p r i s e
Upris e

etc...

they are all technically the same GT