Having work done in the construction industry can be a complex undertaking. You have to find a contractor who can get the project done, and you have to find terms that are negotiable to both sides. In most cases, there are going to be adjustments to the terms of the contract when you are working through the project. These alterations are usually relayed through change orders.
A change order is an addition or omission from the original contract. Both parties have to agree on the terms of the order. There are many reasons why this might be necessary. Something as simple as adding a window to a home's plans or deciding that you want a different type of flooring would require a change order.