Gold jewelry (white, rose, and yellow) is typically stamped with a karat quality stamp. But what do the different stamps really mean? Pure gold is 24 karat. 22k gold is an alloy of 22 parts gold and two parts other metals (typically copper, silver or platinum). Likewise, 18k is made up of 18 parts gold to six parts other metals, and so on. Another way to indicate gold karat is by percentages, or ".585" or ".750". These numbers are the result of dividing 14 by 24, 18 by 24, etc..
Because of the higher percentage of gold, a piece of jewelry made in 18k gold jewelry will cost more than an equivalent piece made of 14k. Jewelry is typically 22k or less, as 24k gold is very soft.
I hope this clarified the differences in gold karats. Just don't get "carat" and "karat" confused!