RecognitionVsRecall

When a user knows exactly what they want, that's Recall. They want to go directly to what they want. On the other hand, often a user doesn't know exactly what they want. They want to look around until they see something that looks promising -- that's Recognition.

Also known as Search vs Browse. Search interfaces are good for recall; browse interfaces are good for recognition.

Both tyeps of interfaces are needed in different contexts and are enhanced by different patterns; you should be aware of both.