Contractors are useful for a variety of reasons. You can hire contractors to remodel your home, build a new home, or work on small projects that you might need. Contractors are going to be specific to a specialty. In other words you can hire a general contractor that is going to oversee the whole project. Then you have trim carpenters that work on trimming your house only. You will want to pick the right contractor for the job you need done.
The best thing to do when you are looking for contractors is to find a general contractor that has subs or a team of men. In this way you are able to get everything you want done completed. General contractors have sources you might not have.