Build processes are key to any project,
you may be already using them without knowing. The easiest way to understand them is to think of the as jobs running in the background minifying and concatenating code. To help with development it may use LiveReload to speed up your coding so you do not have to restart your node server i.e nodemon
The function of a build process is to speed up the site/project and its development. It is also designed to streamline a projects workflow or evolution, in other words it allows the project to improve with much less command line and meta-setup work.
Common tools used to implement this are Grunt and Gulp both Command Line Tools.