What is end-to-end encryption?
End-to-end encryption (E2EE) is a system of communication where only the communicating users can read the messages. This kind of encryption prevents any third party from eavesdropping on your data keeping it safe and private at all times. This is not the case with many other providers including Dropbox, Google Drive, Microsoft OneDrive and many others. For a detailed technical definition of E2EE, lookup on Wikipedia.