A pattern or architecture for applications which involves separation of Model (business) logic from View (output) logic from Controller (form/input) logic. Which should make it easier to support multiple Views from a single set of business logic, among other things.
An alternative summary, which might not even be accurate
HTTP request is sent to Controller.
Controller then calls the View with that data, so the View can render it. (Or perhaps redirects to a View? If so, does it do that via HttpPost to pass the data it already has (can you even redirect with a POST?), or else does it make the View do its own call to get its data?)
Ruby On Rails notes
URI path defines Controller, method/action - like '/store/add_item/'