What is a framework? What does it do? Why do we need a framework?

the Framework is a bit unusual for a large-scale effort, but not entirely unheard of.

Most times, applications will ask for a particular version of the framework to be installed. We'd recommend avoiding installing that particular version, and trying instead to install the most up-to-date version of .NET, assuming your Windows OS supports it. Most .NET packages have backwards compatibility, so an app asking for the 2.0 framework can usually get by with what's packaged into the latest version: .NET Framework 4. Be sure, too, that you're settled up on your Windows Update requests, as there may be relevant system patches that need installing before .NET will fit comfortably on your system.

One problem .NET installations often run into is a need for space, even if your system might not make that explicit. The 4.0 version of .NET for standard 32-bit Windows systems requires 850 MB of free space on your primary Windows drive; a 64-bit Windows system needs 2 GB free, and Windows usually won't ask you if you have space on another partition to spare. If your free space is smaller than these amounts, you'll need to look at your hard drive and free up some space.

Framework is a collection of classes , interface or abstract classes that will enforce other developer to follow your way of writing the code for any application. 

and it's very important as in working within framework it's easy and flexible to maintain your code , and it will prevent the redundancy in code and  you can reuse existing code . and as a result your code will be more organized. 

Entity Framework or EF is an ORM that enables .NET developers to work with relational data using domain-specific objects. It eliminates the need for most of the data-access code that developers usually need to write

it's easy and fastest way to create database and web page with CRUD