You can “like” a film any time to show you enjoyed it, which builds up your Profile and Likes pages. You can rate films (via the film’s page, or by logging it, or using the Actions menu on any poster) to give your friends a better idea of how much you loved (or hated) it — and they’ll see this on your Ratings page and in their activity feed (if it’s part of a review or diary entry). If you provide ratings for films, you can later sort films by these ratings, which is useful for making year-end lists. It’s no problem to use both ratings and likes (or neither).