The pattern "Door" is made up of the patterns "hinge" and "handle" -- and their configuration is what makes the pattern "door"
Let's take the simple example, "door." We all know what a door is -- in fact, doors are so common that it's probably not necessary to write a formal pattern about them. Still, they make a good example for this discussion.
The example of the pattern "door" will illustrate something very important about patterns:
Patterns are parts of other patterns -- and other patterns are part of them.
A door is a thing, but it is useful because it is made up of other things (say, door handle, hinges, screws etc.) and because it is a part of other larger things (say, a room, a house, etc).
You can imagine that a door without a handle or hinges would not be much use. The first time you pushed it, it would just fall over!
Similarly, a door that is not within a room or a house, but just standing up in the middle of a field, would not be much of a door either!
The door is a door because it is related to other things - it is a part of some (larger) things, and it has (smaller) things that are part of it. It is part of a system.
That's what is useful about a pattern language -- it's a flexible way of describing the elements of a system, not just as independent entities, but as they relate to other elements of the system.
So let's see an example of what the pattern "Door" might actually look like. Click on this pattern link: