OAuth is a simple way to publish and interact with protected data

What Company Is Offering:
OAuth is a simple way to publish and interact with protected data. It's also a safer and more secure way for people to give you access. They've kept it simple to save you time.
OAuth , it allows you the User to grant access to your private resources on one site (which is called the Service Provider), to another site (called Consumer, not to be confused with you, the User). It is intended to solve this problem by allowing users to give services a valet key to their identities, rather than full access.

How Is It Different:
While OpenID is all about using a single identity to sign into many sites, OAuth is about giving access to your stuff without sharing your identity at all (or its secret parts).OAuth attempts to provide a standard way for developers to offer their services via an API without forcing their users to expose their passwords (and other credentials).

What For:

Many luxury cars today come with a valet key. It is a special key you give the parking attendant and unlike your regular key, will not allow the car to drive more than a mile or two. Some valet keys will not open the trunk, while others will block access to your onboard cell phone address book. Regardless of what restrictions the valet key imposes, the idea is very clever. You give someone limited access to your car with a special key, while using another key to unlock everything else.

Everyday new website offer services which tie together functionality from other sites. A photo lab printing your Flickr photos, a social network using your Google address book to look for friends, and APIs to build your own desktop application version of a popular site. These are all great services – what is not so great about some of the implementations available today is their request for your username and password on the other site.
More at:http://oauth.net/