What is the difference between an estimate and a fixed quote?

An estimate is a considered guess based on what can be seen; a quote is a price you can hold someone to. A number given over the phone before anyone has measured is an estimate however it is labelled. A fixed quote follows a walkthrough, names the materials and the scope, and states what would change it, which is normally limited to what is found behind a wall or a change you ask for. Ask which one you are being given and get the answer in writing.