What exactly is included in contractors' estimates

[Ramon Luna]

Hi all. Im curious to know, when your contractors' give you a 10k estimate (for example) to rehab the kitchen in your house, what exactly does that include? How does he/she know the materials you want in the kitchen. Higher end finishes would obviously cost more. Or, when asking for an estimate do you tell your contractor which materials you are planning to use? Or does the estimate just include labor?