Answer 1

You dont can google it? Your browser dont work?
REST. This abbreviation can be deciphered in the following form: presentation of data to the client in a format convenient for him. It is very important to remember that REST is not a Protocol, but an approach, an architectural style to writing application interfaces.
To put it even more simply, REST is an architectural style, and RESTful API is its practical embodiment, and the more an application meets the REST style criteria, the more RESTful it is.
RESTful API is reduced to four basic operations:
receiving data in a format convenient for the client
the creation of new data
data refresh
delete data
REST functions on top of the HTTP Protocol, so it is worth mentioning its main features. Each operation above uses its own HTTP method:
GET-receive
POST – creation
PUT – update, modification of
DELETE-delete
All these methods are collectively called CRUD (create, read, update, delete) – (create, read, update, delete) operations.

Answer 2

We have a series of lessons on SoloLearn too about REST
https://www.sololearn.com/learn/10391/?ref=app

Answer 3

In fact, REST has a single, consistent common interface for querying, for example, databases, which is its most important advantage.