X uses Y in its solution
This relationship makes clear, that Y can be used as a part of the solution of X. The description of X can refer back to that of Y, in order to be shorter and easier to understand.
Tools supporting the design pattern approach can profit from this information; the relationship can be checked in existing designs. Design patterns like Y can be visualized as blocks without internal implementation details in order to raise the abstraction level.
X is similar to Y
Design patterns related in this way address similar problems. When searching for a design pattern which solves a certain kind of problem, first of all you can look at a family of similar design patterns addressing this kind of problems. Secondly, you use the one which meets your requirements best. Thus, this relationship supports the retrieval of design patterns.
X can be combined with Y
When one has already applied a design pattern in a system, relationships of this kind can help in finding other design patterns which are useful to combine with the existing one. Thereby, the retrieval of design patterns is supported. Several design patterns related by this relationship may also be used as larger building blocks in design, thus raising the abstraction level.

Click here to have alook @ design patterns: Elements of Reusable object oriented software.

Just a glims of what this PDF talks in form and slide.