Vaishnavaite followers refer to this verse as the Charama Shloka, and it is one of the Rahasya Traya or three secrets of Vaishnavism.

"Abandon everything else and just surrender unto me. I shall deliver you from all your sins"

Why should a believer of Krishna surrender to HIM alone? So does it mean that there is nothing else?

The operative or critical word in the sloka is "ekam" which means "only". Why does HE say "ekam"?

It means that the way to reach HIM is to follow his teachings, HE guarantees you that HE will release you from all sins you have committed (knowingly or unknowingly).

But it also additionally, means that whilst the destination is HIM, the way to reach is also through HIM. The only place in the universe where the path and the destination are the same.

The verse, hence basically means, Surrender yourself ONLY to ME to REACH ME.