I am new on AWS cognito. I read the aws cognito documentation and search on internet. On some places I found that AWS cognito is use for user login and register and somewhere I found that cognito is used for data sysncronization with devices and server. So now I am totaly confused that what is the basic use of cognito and what is the best use of cognito either user login/register or data syncing.
Thank you
Short ans: Both :)
A good place to start would be to go through the FAQ's https://aws.amazon.com/cognito/faqs/
AWS Cognito is a collection of following services and functionality in summary.
AWS Cognito Userpools- Identity Provider used for application login, single sign on. It is also possible to integrate external identities which supports SAML (e.g; Microsoft Active Directory) and Social Identities (Google, Facebook, Amazon).
AWS Cognito Federated Identities - Identity Broker that delegate other identities permission to access AWS via AWS Roles. (For example, you can connect Userpools to this and configure who logs in through the particular Userpool will get AWS permission to create a EC2 instance).
AWS Cognito Sync - This is another functionality to provide offline syncing support (Specially for mobile apps) where its possible to keep a data store for each user which can be sync with the backend counterparts in AWS which could integrate with other AWS services.