It is well-known that Microsoft claims that Android infringes on Microsoft's patents; Microsoft themselves explain this on their website, saying they "simply cannot ignore infringement of this scope and scale", and that:
The Microsoft-created features protected by the patents infringed by the Nook and Nook Color tablet are core to the user experience.and
Our agreements ensure respect and reasonable compensation for Microsoft's inventions and patent portfolio. Equally important, they enable licensees to make use of our patented innovations on a long-term and stable basis.
However, what has never been known (until now), is precisely what those patented innovations are. As Mary-Jo Foley observed more than 6 months ago, Microsoft refuses to identify the patents, and why it believes Android infringes upon them, unless a Non Disclosure Agreement is signed agreeing not to reveal that information.
Barnes & Noble apparently refused to sign that agreement, and instead found counsel to represent them, and now the information about the patents in question is no longer a secret.
According to the Barnes & Noble filings, the primary Microsoft patent which Android infringes is a 16-year-old patent (U.S. Patent 5,778,372), which patents:
A method of remotely browsing an electronic document residing at a remote site on a computer network and specifying a background image which is to be displayed with the electronic document superimposed thereon comprising in response to a user's request to browse to the electronic document.
Apparently, changing the background on your screen when a document is displayed is patented.
I understand software quite well.
I don't understand law at all, and specifically I don't understand intellectual property law.
However, I find the GrokLaw analysis of the Barnes & Noble v. Microsoft dispute absolutely fascinating.