A a codebase (or code base) is a collection of computer instructions known as source code written in one or more programming languages used to build a particular software system, application, or software component.
A codebase from a business perspective represents an asset could easily run into millions of lines of code representing person centuries of effort.
Also, IT staff that have been with the organization for a while tend to develop a knowledge of the code base, and this enables them to make improvements and fix bugs and add enhancements easily.
