A deliverable is the product of work done on a project; the finished result of a step of work. Deliverables are sometimes described as inputs or outputs. One person's outputs, are the next person's inputs, until the project is complete. Any unique and verifiable product, result or capability to perform a service that must be produced to complete a process, phase or project. Often used more narrowly in reference to an external deliverable, which is a deliverable that is subject to approval by the project sponsor or customer.

There are three types of deliverables. The first is a stage or phase, which is a large, defined piece of a project that ends with a clearly defined set of deliverables. The second is a milestone, which is a defined set of deliverables due at the end of a phase or stage. The term comes from the markers along  roads that tell us how far we've come-and how far we still have to go. The PMI has a similar definition of a milestone:  a significant point or event in a project, usually completion of a major deliverable. Milestones are part of the work process  and can be looked at in terms of reporting project status.

The gate in a deliverable is the review process at the end of a phase where it's ensured that the deliverables are all in good shape and a decision is made whether or not to continue the project. The gate can also be placed at the beginning of the first phase to make sure everything is lined up and the project is ready to go.