Double Diamond

Double Diamond is an iterative design process made up of four stages; Discover, Define, Develop, and Deliver.

Double diamond process
The google homepage

Discover

The first diamond helps you understand what to focus on. This is made up of research including User Interviews and Usability Testing.

Define

The learnings from the research during the discovery stage can help you to define the what you need to be working on.

Develop

The second diamond is about designing and creating solutions. Collaboratively creating ideas and prototypes which will be used for testing.

Deliver

This last stage involves testing out your different solutions to learn which ideas to scrap, and which ideas to improve upon.