Martin Fowler: Continuous Integration is a software development practice where members of a team integrate their work frequently, usually each person integrates at least daily – leading to multiple integrations per day. Each integration is verified by an automated build (including test) to detect integration errors as quickly as possible. Many teams find that this approach leads to significantly reduced integration problems and allows a team to develop cohesive software more rapidly.
Some posts about Continuous Integration for further reading:
Continuous Integration
How and why do I set up a C# build machine?
Best Continuous Integration Setup for a solo developer (.NET) [closed]
Continuous Integration for Everybody
Jhonatan Tirado 