The term Gestalt may be defined as an object, idea, or experience as being more than the sum of its parts. When you put the parts together, you get the whole - in other words, you get the Gestalt.
Gestalt is the basis of Gestalt Psychology, which is the study of how people integrate and organize perceptual information (information they perceive - things they see, hear, etc) into meaningful wholes.
For example, can you tell what this is?: 8> )
The reason you may be able to recognize a face is because you're able to see an overall form (a face) just by putting a few symbols or shapes together. In other words, you see the Gestalt, not just the symbols. This is incredibly useful but can sometimes lead to problems such as illusions or visual tricks.