Complex sentence: Contango is a futures market term: it means an "upward" sloping forward curve (as in the normal yield curve): one says that the forward curve is "in contango" (or sometimes "contangoed").
Split into simpler sentences: Contango is a term used in the futures market to describe an "upward" sloping forward curve (as in the normal yield curve). One says that such a forward curve is "in contango" (or sometimes "contangoed").