[1] Thus, interaction design patterns are a way to describe solutions to common usability or accessibility problems in a specific context.
[2] They document interaction models that make it easier for users to understand an interface and accomplish their tasks.
Patterns are ways to describe best practices, explain good designs, and capture experience so that other people can reuse these solutions.
The Apple Computer's Macintosh Human Interface Guidelines also quotes Christopher Alexander's works in its recommended reading.
Alexander envisioned a pattern language as a structured system in which the semantic relationships between the patterns create a whole that is greater than the sum of its parts, much like the way that grammatical relationships between words make language meaningful.