Entity Framework is an object-relational mapper (ORM). It maps your .NET code objects to relational database entities. As simple as that. Now, you don't have to concern yourself with scaffolding the required data-access code just to handle plain CRUD operations.
When the first version of Entity Framework was released with .NET 3.5 SP1 in August 2008, the initial response wasn't that great, so much so that a group of developers signed a vote of no confidence with regards to the framework. Thankfully, most of the raised concerns were addressed and the release of Entity Framework 4.0, together with .NET 4.0, put to bed a lot of the criticisms around the stability of the framework.
Microsoft then decided to take .NET cross-platform ...
