are required for all projects initiated by new clients and are negotiated on a project-by-project basis.
for existing clients are negotiated on a project-by-project basis.
protect both the client and the freelancer.
may be as formal as a written document or as informal as an email-and-response.
specify specific expectations on the part of both the client and the freelancer, including: deliverables, deadlines, pricing structures, payment expectations, etc.