What does it mean to "Like" something on Facebook?

What does it mean to "Like" something on Facebook?: "Well, first of all liking"only works if, in fact, you have a Facebook account.

If you don't have a Facebook account, then liking is simply not an option for you;
You basically won't get the advantage of whatever it is the merchant is hiding behind the request to have you like their page."

'via Blog this'