The concept of a pattern is simple to define. A pattern is something that you did in the past, was successful, and can be applied to multiple situations. Patterns capture experiences in software development that have been proven to work again and again, and thus provide a solution to specific problems. They are not invented: they arise from practical experience.
When many programmers are trying to solve similar problems, they arrive again and again at a solution that works best. Such a solution is later distilled into a solution template, something that we programmers then use to approach similar problems in the future. Such solution templates are often called patterns.
Good patterns are problem and language agnostic. In other words, they apply to C++ and Delphi, and to Haskell and Smalltalk. In practice, as it turns out, lots of patterns are at least...
