Answer:
Project templates are molds of how a project should look like, and is the starting point for the project and forms the overall basic design.
When managing a project there are many different documents that need to be produced along the way, as the project progresses from start to finish - e.g. Project Charter, Project Plan, Business Case, Implementation Plan. Project templates are simply blank pro formas that help a project manager initiate these documents. They provide a pre-built structure to each document, as well as suggestions / prompts as to what they should write in each section. Each project template serves a different purpose in the project.