I've seen a number of questions about lenses, and I've picked up enough to work out that it's something to do with the Unity shell in Natty, but I haven't really worked out exactly what is meant by it. So can someone give me (or link to) a good description of what a lens is?
It is a graphical interface for a task, it is also linked in with the dash for search results. for example when clicking the application lens it shows the apps in a nice, slick interface , with other results for like app to download and most frequent apps.
If you hover over the "lenses" tag below your question, you'll see this succinct description: