An easy question to answer easily, a hard question to answer in depth. Another name for the emotivist viewpoint is, awkwardly enough, the "hurrah/boo theory." It's not very popular these days.
Emotivists believe that many statements are factual but with opinions sort of tagged on. They would consider a statement such as "You shouldn't have hit him" to contain two parts: "You hit him" (a factual statement that is verifiable) and "I don't think hitting is right" (a part of the sentence that adds the speakers emotion to it. From this, you can see where the "hurrah" or "boo" part comes into play...people often use factual statements with a personal judgement added into them. You are, in fact (according to emotivists) trying to convince the other person of your moral viewpoint when adding in such statements. There is a twinge of judgement thrown in there.
Compare that to subjectivists who would say that the statements "It is wrong to hit" and "It is right to hit" are sort of equal because they express the opinion of the speaker (though on opposite sides.) It is a subtle difference but an important one.