A builder is someone you hire to build your house, correct? Well, yes and no. It has been said that when you hire a builder you are really hiring four people: the builder, the builder's crews, the builder's subcontractors, and the builder's suppliers. What this means is that most builders do not build houses by themselves, but hire outside subcontractors to do part of the work--plumbers and electricians are good examples.
Except for a few very large builders who have the requisite staff and tradesmen on their payroll to build a house from start to finish, most builders are not only builders, but also general contractors, or GC's as they are known in the trade. That is, they hire and schedule other specialised subcontractors to work for them in the building of your house.
If you do a good job of hiring a builder, things should go reasonably smoothly. If you don't, then you are going to put yourself in the unenviable position of supervising your builder. And, if you haven't been through the building process before, there won't be enough hours in the day for you to learn all you need to know to have a chance of doing this well.