A project notebook is a complete documentation of a project's details. This documentation includes sketches; information from books, discussions, and meetings; and your own thoughts. Unlike a formal report, a project notebook is more informal. In fact, you might consider it to be a journal where you also record your frustrations and successes about a project. A project notebook may also be called a design notebook. Like the project notebook, a design notebook includes similar entries, but concentrates more on design evolution.

The main purpose of a project notebook is to record your work as it progresses. This way, you can go back to the work you did months before and reconstruct, interpret and evaluate the processes you carried out to accomplish your project.