Build systems are tools used for compiling source code and assembling/packaging the results.
Build systems covers a wide range of tools that are used to compile/assemble/transform source code into executables, libraries, and other artifacts; these tools can include (but are not limited to) e.g. make
, ant
, gradle
, maven
, etc.
These systems can also be covered/described by terms like "build automation", "build servers"; more information on tools of this kind can be found on Wikipedia.