Something that's improved has gotten much better than it used to be. An improved menu at a restaurant has more choices — or at least more of your favorites.
The adjective improved is good for describing things that are made to work better or have been updated in some way. An improved piece of computer software might be faster or more efficient than the old version, and if you have an improved outlook on life this morning, you're feeling more optimistic and happy than you were yesterday. The Anglo-French root is emprouwer, "to turn to profit."