Liking is a secret action which allows you to show your interest for someone who has caught your eye! You’ll know if you’ve Liked each other only if it is mutual.
A SuperCrush is similar to a Like except that when you send a SuperCrush to someone, this person receives a notification. It is the best way to get your profile noticed! It is a paid feature.
A Crush is the result of a mutual Like or SuperCrush (or a Like and a SuperCrush) between two profiles: it means that they're both interested in each other and can start exchanging messages.