A Protectorate is an autonomous territory that is protected diplomatically or militarily against third parties by a stronger state or entity. 
The protectorate retains formal sovereignty and remains a state under international law, but in exchange for this, they usually accept specified obligations that vary depending on the nature of their relationship.

What is the difference between a colony and a protectorate?

A colony has no control over its internal affairs and is a part of the same nation as the colonial power. A protectorate continues to be an independent state, with its external affairs controlled by the protector country, or countries.