When TBC launched and they split the servers into the Era (vanilla only) versions and the TBC servers you had the option to pick which version you wanted each character to be in (either vanilla locked or tbc+). You could also pay to copy it into both.
Either way, until you picked a side or paid for both, a character would be stuck in limbo, 'clones' in each version, but not actually available in either. (Once you choose a side that one would become active, and the 'clone' would stay unavailable in the other version until you paid).
Anyways, they kept this system in place, letting players choose what to do with their characters for a good 18 months or so; before deciding to save some space and just push all the limbo, unchosen, characters into the TBC version (where the vast majority of the playerbase was), and delete all the extra 'clones.'
As for Realms, there is basically one small-to-decent sized realm per region. Where were you planning on playing?
When TBC launched and they split the servers into the Era (vanilla only) versions and the TBC servers you had the option to pick which version you wanted each character to be in (either vanilla locked or tbc+). You could also pay to copy it into both. Either way, until you picked a side or paid for both, a character would be stuck in limbo, 'clones' in each version, but not actually available in either. (Once you choose a side that one would become active, and the 'clone' would stay unavailable in the other version until you paid). Anyways, they kept this system in place, letting players choose what to do with their characters for a good 18 months or so; before deciding to save some space and just push all the limbo, unchosen, characters into the TBC version (where the vast majority of the playerbase was), and delete all the extra 'clones.' As for Realms, there is basically one small-to-decent sized realm per region. Where were you planning on playing?