Celebrate brings to mind a festive, happy occasion. Joy is being happy and cheerful. Revel is the root word for "revelers" which means party goers(noun). But the word revel can also be used as a verb, for example: "Revel in the moment" or "savor the moment." Rejoice is very similar in meaning to joy. For example: The couple rejoiced when a new baby was added to the family.

Out of them, joy is a noun that is an emotion meaning happiness. The others are verbs. To celebrate and to rejoice mean basically the same thing, but celebrate is used a little more often. Revel isn't used much. It has a similar meaning but is closer to "to take pleasure in looking at."