To salivate is to drool, or to produce saliva. People also figuratively salivate over things they desire.
There are two related types of salivating. The first is simple: when you salivate, you produce saliva in your mouth. People salivate when they smell something delicious cooking or are hungry. You can also describe someone as salivating — metaphorically — over an attractive woman, a handsome man, an expensive car, a high-paying job, or anything else that's desirable. You can also say that people drool over these things they want, although they’re not literally drooling.