Continuous Integration (CI) is an Extreme Programming (XP) practice where members of a delivery team frequently integrate their work (e.g. hourly, or at least once daily). Each integration is verified by an automated build, which also performs testing, to detect any integration errors quickly and automatically.
The main goal of CI is to avoid the point in production when members on a delivery team integrate their individual code. In traditional software development environments, this integration process is rarely smooth and seamless, instead resulting in hours or perhaps days of fixing the code so that it can finally integrate. Continuous Integration (CI) aims to avoid this completely by enabling and encouraging team members to integrate frequently (e.g., hourly, or at least daily).
The principle benefits of CI are significantly reduced integration problems and better team coordination leading to higher-quality software being released more rapidly than in traditional software development environments.
See also: Breaking the Build