React Hooks are introduced react 16 with functional component. There are multiple built in react Hooks which we commonly used during application.
Aggregation in mongodb is refered as the process of performing different type of operation on multiple documents with in a collection. This is done by using pipeline, which is made up of different stages. A stage output is input for another stage.
Access Token:it is used to access the resource from server by using the token. But this token had a shorter time validy which can range from 15 minutes to 1 day. These access token can't be used after their validity time expired.
Refresh Token:refresh token is used to refresh something. Refresh token has longer validity time than Access token. It can range from 5 days to months or year. This refresh token is used to refresh the Access token as access token will be expired after sometime. Refresh token provides extra layer of validation for Authentication.