Builds are the functions that you make inside the Busywork editor. By connecting building blocks you decide what your function is going to do. Once deployed the functions can be run by sending a HTTP request to the function URL.
Builds are a series of operations that are applied to request data, when the function is run. Operations are represented by building block in Busywork and allow you to make functions that read and write from a database, perform some action based on a condtion or trigger an action in a third-party service such as Mailchimp.