The <ahref="licenses/mit">MIT License</a> is a permissive license that is short and to the point. It lets people do anything with your code with proper attribution and without warranty.
The <ahref="licenses/apache/">Apache License</a> is a permissive license similar to the MIT License, but it provides a patent license for any code that infringes on a contributor’s patents.
The GPL (<ahref="licenses/gpl-v2">V2</a>, <ahref="licenses/gpl-v3">V3</a>, or <ahref="licenses/agpl">Affero</a>) requires that folks who modify your code also license their changes under the GPL. V3 is similar to V2, but adds a restriction restricting use in hardware that forbids software alterations.