Persona lets you log in to websites using only your email address! Persona lets you prove your identity to websites through your email address without giving them any passwords.
This works similarly to how you prove your identity when you show someone your ID: websites can easily verify that your ID is authentic and that you really are the person it was issued to.
What are the benefits of Mozilla Persona?
You can use one easy-to-remember log in for all sites that support Persona.
You never have to trust a website with your password because they never know it. Also, your password can't be stolen if one of those websites gets hacked.
You can use Persona with as many email addresses as you want. This lets you keep your various online personalities (school, work, home, etc.) separate.
Persona doesn't let your email provider track what websites you visit.