In basic terms, carat weight is the weight of a diamond. One carat is equivalent to 100 points; so for example, a .75 carat diamond is 75 points. All things being equal, the more a diamond weighs the more valuable it is.
Diamonds can range in size from a fraction of a carat to several carats. The price per carat increases rapidly with size, and you can expect to pay a premium for stones that are above one carat weight. That’s why a single 2-carat diamond will cost substantially more than two 1-carat diamonds. In jewelry pieces with more than one diamond, the carats may be described in terms of total carat weight (TW). This is the combined total weight of all the diamonds in the piece.