Programmers are responsible for developing code to build products. In an interview context, expect to be quizzed on your technical skills through different kinds of computing problems or brainteasers. The specific questions you are asked will depend on what type of programming position you are looking for. Try researching a specific discipline such as web development, application development, or system development.
I was asked to represent the application architecture on my previous project, with a simple diagram that someone with no background in it could understand