If you choose someone or something from several people or things that are available, you decide which person or thing you want to have.

If you choose to do something, you do it because you want to or because you feel that it is right.

If there is little to choose between people or things or nothing to choose between them, it is difficult to decide which is better or more suitable.

The chosen few are a small group who are treated better than other people. You sometimes use this expression when you think this is unfair.