What is Oauth?
OAuth is an open standard to authorization. OAuth provides client applications a 'secure delegated access' to server resources on behalf of a resource owner. It specifies a process for resource owners to authorize third-party access to their server resources without sharing their credentials.
OAuth (Open Authorization) is an open protocol for token-based authentication and authorization on the Internet.
OAuth, which is pronounced "oh-auth," allows an end users’ account information to be used by third-party services, such as Facebook, without exposing the user's password.
OAuth can be used as an authorizing mechanism to consume secured RSS/ATOM feeds. Consumption of RSS/ATOM feeds that require authentication has always been an issue. For example, an RSS feed from a secured Google Site cannot be consumed using Google Reader. Instead, three-legged OAuth can be used to authorize Google Reader to access the RSS feed from that Google Site.
1. You can use the same login for web as well as native(mobile) apps
2. You don't have to save session information on the server
3. You can easily set expiry date in token itself
1. You can't save additional information about user on the server
Video Tutorial for What is Oauth