The main purpose of a question and answer document is to make it easy for readers to find answers to their question. It is easier to match one's question in an index, than to run a number of searches on a pile of documents. So in essence a FAQ is a tool for readers to get an answer quickly.

But make sure that the FAQ is short and focussed. There is very little structure in this list and the simple question/answer format may be too easy to pour any information in. Instead documentation should be structured and goal orientated.