There are over half a million words in the English language. Our tongue has a marvelous elasticity, a broad perspicacity, a nearly inexhaustible wellspring of mellifluous, trenchant, and piquant words, providing our speech with crystal clarity and minute precision.
Yet, too often, we make the mistake of using certain words as synonyms which, rather than naming the same thing, actually introduce fine distinctions in a concept. This ain't no help to nobody. To wit...
These three words are often confused and misused, in secular media, in everyday conversation, and even by priests and theologians. Let's define each so we can use them correctly in the future.
Chastity "means the successful integration of sexuality within the person and thus the inner unity of man in his bodily and spiritual being." (CCC 2337) In other words, chastity means living out your sexuality in accordance with your state of life (e.g. not having sex if you're not married), and not abusing your sexuality in a way that's incongruous with the nature of the sexual act (e.g. self-gratification, homosexual acts, etc.). People often use "chastity" and "celibacy" interchangeably; all too often you hear someone say that "Priests take a vow of chastity." Because they equate chastity with celibacy, people tend to think that chastity is something only priests and religious are called to, which is not the case: everyone is called to live chastely. Everyone is called to live out their sexuality in accordance with their state in life. Well, what's celibacy, then?
Celibacy is the permanent professed state of refraining from marriage. Priests make a promise, and religious take a vow, to remain celibate for their whole lives, in keeping with their vocation. Celibate does not simply mean "not having sex;" so when the ladies' man character in a movie says, "Man, I've been celibate for weeks, I haven't had any action," or when your friend says, "I haven't had a girlfriend for months, I've been celibate all this time," they're using the term incorrectly, unless they mean that in the brief period in question they had made a permanent commitment to never marry. Which is unlikely, given the context. So, if not celibacy, what's the word we want here?
Continence is refraining from sexual relations. This is what the ladies' man character should use instead of "celibate." Now naturally, since in the Church's understanding of human nature it's inappropriate for those who aren't married to have sex, the state of celibacy requires sexual continence. But sexual continence is required of everybody who isn't married, celibate or dating or single or whatever. So we shouldn't use "celibate" as some shorthand for "continence."
So, let's get some practice here: Monks and nuns take a vow of celibacy, meaning they promise never to be married. In order to live chastely, that is, live according to their state in life, the celibate person practices continence, that is, doesn't have sexual relations. Jack and Jill are planning to get married, so they aren't celibates, but still, until they do get married, chastity requires continence.
I hope this helps!