All of the emails you send and receive can be intercepted and read by your email service provider.
Proton is a privacy and freedom based software company in Switzerland. They have many different software solutions, and are very well known.
So well known, that they have over 100 MILLION people and businesses signed up and using them.
Proton uses End-to-End encryption, which means that no one (not even Proton) has access to your information.
They believe that privacy and trust are formed through transparency, that’s why all of their applications are open source and available to audit.
Proton Drive is their online storage service. They store your data on their end-to-end encrypted servers, that follow Swiss privacy laws. You can think of it as a “digital Swiss vault”.