app user enters email → app sends link to email → user clicks & logs in to app.
as an alternative to 3rd party OAuth login (ie facebook login etc).
Its inconvenient for my app’s users to remember passwords just to login to my app. Without depending on Facebook etc, this simplifies the UX so that all they have to do is enter a valid email address that they own and then click a link. In the process, this also verifies their emails automatically.