Compiled set of commands written for a computer or software that describes how a program works.
Source code is a compiled set of commands written for a computer or software to work out. The code is written in plain and readable text using a programming language. This programming language is then converted into machine language by a translator, thus enabling the computer or software to perform the written commands.
A source code can be likened to a manual serving as a guide on how the software works. Depending on the kind of software undergoing development, the source code is useful for fixing bug(s) affecting it, thus preventing any further malfunction in the anticipated operations of the software.
A lot of platforms and developers make their source codes proprietary, meaning others don't have access to it. Some release their source codes to the public to facilitate more development or use of a new technology.