eli5 What is the difference between user to user encryption and user to server encryption?

Question

In context to Whatsapp and Signal using User to User & Telegram using User to Server ( correct me if I’m wrong if not this)

In: Technology

Answer 1

Telegram uses user-to-server encryption by default to support its multi-device architecture, but you can also use its “secret chat” feature for user-to-user (end-to-end) encryption.