Chastity refers to the refusal of any form of erotism and carnal pleasure, and of any impure thought. It’s a form of purity (see purity).
One makes a chastity vow for several reasons: one remains chaste until the wedding or decides to devote his life to a god in a monastery or a couvent.
If we consider chastity as a refusal of erotism, one can remain chaste even after getting married which means that they only have sex to have children and not for pleasure.
We can also be chaste only because we do not feel attracted by any form of carnal pleasure.
In many cultures chastity is considered as a great quality, especially for women. A woman who’s chaste and modest is considered as honorable (cf honour) and people think that she will be a good wife and mother, whereas a woman who isn’t chaste is seen as vulgar.
Chastity can also refer to pure beauty (cf beauty/purity), without any eccentricity or artifice : for example, the beauty of the shy, of a sunset...
This value is mostly for those who are religious, chastity is encouraged in many religions, but it’s also to those who refused any form of carnal pleasure for personal or spiritual reasons.