The difference between circuit breaker and relay

[ROSELJR]

A relay is an electrical appliance that turns on or off the 
controlled output circuit when the input quantity (such as 
voltage, current, temperature, etc.) reaches a specified value.
For example, a circuit breaker is the main switch of the light 
switch at home, and it will automatically trip when the current 
reaches a certain value... Why do many people think they are not 
comparable?
What is the essential difference between them?
Here's the introduction of relay: 
https://www.utmel.com/blog/categories/relays/what-is-relay