The main purpose is early detection of skin cancer and melanoma. Mole maps are often used by dermatologists or given out for patients to use.
The interface presents four zoomable views of the different sides of a human body. You can pick to use a male or female body map on the settings page.
The detail page for each mole provides quick access to a built-in guide with pictures of benign and malignant moles. It's good to be familiar with your body and to have an idea of what constitutes an atypical mole.
Tapping a spot adds a new mole. You can edit and delete spots by tapping them again. You can keep notes on your moles and type a custom name instead of the default one to help you recognize a mole. You can also flag a mole as a concern to make it easier to bring up issues with your doctor.