The Meteor build system is the actual command line tool that you get when you install Meteor. You run it by typing the meteor command in your terminal, possibly followed by a set of arguments. Read the docs about the command line tool or type meteor help in your terminal to learn about all of the commands.
What does it do?
The Meteor build tool is what compiles, runs, deploys, and publishes all of your Meteor apps and packages. It’s Meteor’s built-in solution to the problems also solved by tool