What should a e-mail address confirmation e-mail say?

I'm sending out an e-mail containing a link to prove the user had registered with an e-mail address they have access to.

1. What is the name of such an e-mail? Verification e-mail, confirmation e-mail, account activation or something else? In a similar sense what is the name of the link in the e-mail?

2. What should the e-mail say? I want to make this accessible to non-technically inclined users.

3. What should the subject of the e-mail be?