It is important to ask the client questions in order to get specific details about what they really want. When you do this, you satisfy their need.
*For example, let's say you work at Subway
A man comes in and he says, "I want a sandwich"
Okay... but what kind of sandwich? A BLT, Ham and Cheese, Roast Beef, Peanut Butter and Jelly?
You need to ask questions so you can fulfill their request to the best of your ability and make sure there are no problems.