Costs associated with a building project generally fall into two categories:
Soft costs are services, expenses and fees. Some examples include design, structural engineering, energy code consultants, contractor profit and overhead, planning department review fees, building permit fees, utility and infrastructure impact fees. They can also include insurance costs, temporary protection for your house and yard, weather protection, and more.
Hard costs cover materials and labor. Some examples include: lumber, concrete, roofing, windows, subcontractor labor, furnishings, fixtures, appliances, window coverings, and landscaping. Everything that goes into the final product has an associated dollar sign. As you assemble your project team, your sensitivity to cost fluctuations will be a big influence, and it may also direct you to a particular type of project delivery. For example, your architect can explain how design-build or a design-selected contractor approach can reduce risk of cost shifts.
A final note about costs: No matter how well you plan, there are always UNEXPECTED COSTS associated with a construction project. It is always recommended that your budget incorporates contingencies to account for these! (10% is common)