Like is an action on Facebook. It allows you to show your approval of a Status, Picture, Page or Comment. So far, you can not "like" a "like". Like can be used as a verb or a noun in this case. There does not exist a dislike at the moment, but it has been heavily requested. Liking something often makes that object eligible to appear in your Notifications even if you did not comment on it or are not tagged in it.