A build tool takes care of everything for building a process of application/software. Main aspects
(i) Generates source code (if auto-generated code is used),
(ii) Generates documentation from source code
(iii) Compiles source code,
(iv) Packages compiled code into JAR of ZIP file
(v) Install the packaged code in local repository, server repository, or central repository
Some of build tools: ANT, MAVEN(Java), MS Build(c++, .NET), Pybuild(python)