What is context?

So far, from what I've seen around the Internet, "context", refers to the reasoning behind something existing. I have to analyze the context of several of productions this year, including websites, movies, and books.
At the moment, I'm analyzing the context of a program,Skype, so far, my main idea for the context of Skype, is "Video Conferencing" - well, thats the main idea, isn't it?
Further on, I discuss how the context has changed throughout it's development, and now real phone calls can be made from computer to phone. The context has changed, developed.

I need some tips on writing about verbal context. For now, all I have is that Skype uses a range of persuasive language, which makes users interested in what called 'buying credit'.
Also, if you could reassure that my ideas for social context are correct, it'd be great too:

• Advertising
• 'Skype me' - use of the application name within everyday social activities (tell me if you think this is more of a verbal context - I was kind of stuck on this, so I thought I'd throw it into social)

I appreciate your help guys!