A code retreat is a one-day intensive coding session where participants pair up to work through challenges and practice coding techniques. The goal is to learn through pairing with others, extend comfort zones, and experiment with practices like test-driven development. The day consists of short coding sessions focused on a problem like Conway's Game of Life, using different constraints each time like limiting data structures or writing tests first. Participants learn principles like keeping code simple, single responsibility, and continuous integration. The retreat aims to accelerate learning through collaborative problem-solving in a fun, no-pressure environment.