What does the phrase "Facebook has an API for .Net" mean?

[Work Aholic]

What do you mean by, create a Facebook application in this context?

[twinsfan3488]

An API is a set of routines, protocols, data structures, etc. used to support creating applications.

.Net is referring (I'm assuming here) to Microsoft's .NET framework. .NET is a software framework:

http://en.wikipedia.org/wiki/Software_framework

that is used on Windows computers.

[Aaron]

It means you can use any .NET language (C#, VB etc) to write an application that runs on the Facebook website.

[API = Application Programming Interface]

[Liars never lies]

.NET Framework is a set of tools and such that is developed by Microsoft for program development. The phrase simply means you can make an application that uses Facebook in one way or another through its API in one of the languages supported by .NET.