Redux-saga and redux-thunk are redux middleware libraries, that are designed to make handling side effects(asynchronous things like data fetching) easier to manage and better at handling failures.
The difference of those 2 libraries stands on processing the data fetched from back-end api.
Redux-thunk handles the data in a callback function and redux-saga uses async-await functions so that the code execution is suspended until asynchronous execution is completed and data is returned as the result of function(It’s similar to PHP).
Here is a great guide about redux-saga and redux-thunk
https://engineering.universe.com/what-is-redux-saga-c1252fc2f4d1
