Front-end and back-end
In their most general meanings, the terms front end and back end refer to the initial and the end stages of a process flow. These terms acquire more special meanings in particular areas. The general idea is that the front end is responsible for collecting input from the user, which can be in a variety of forms, and processing it in such a way that it conforms to a specification that the back end can use. The connection of the front end to the back end is a kind of interface.