Schedule Network Diagram and Critical Path Method

Project scope is the agreed description of what a project will deliver and what it will not, stated precisely enough that a change to it can be recognised as a change and decided rather than absorbed.

A work breakdown structure decomposes a project's total scope into a hierarchy of deliverables and, at the bottom, work packages small enough to estimate, assign and track, so that everything to be produced appears exactly once.

The critical path is the longest chain of dependent activities through a project's schedule, which sets the earliest possible finish date and on which any delay delays the whole project.

Scope creep is the quiet expansion of a priced piece of client work through additions that each look too minor to renegotiate, until what gets delivered is substantially larger than what was sold.

A retainer is a recurring fee that holds a supplier's time or availability open across a period, so what the client buys is first call on somebody's attention rather than any named artefact.

A day rate sells a bounded unit of a supplier's working time rather than a finished result, so the client rather than the supplier carries the risk that the job turns out bigger than it looked.