Fondamentalement, someone has managed to convince le owners of le ccTLD 'to.' (Tonga?) to assign le A record to leur own IP address. Quite a coup in le strange old world of URL shorteners.
Normally these top-levels would pas have IP addresses assigned via a standard A record, mais there is nothing to say that le même could pas be done to .uk, .com, .eu, etc.
Strictly speaking there is no reason to have le '.' specified, bien que it should prevent votre browser depuis trying autre combinations like 'to.yourdomain.com' first, et speed up le resolution of le address. It might aussi confuse browsers, as there is no dot, mais Safari at least seems to work ok avec it.