This question is a bit ambiguous as there were a few features that were added and any could be perceived as distinguishing depending on what you look for in your OS. I do believe this is in reference to the Wikipedia article on Windows 2.0 though as the first two listed features make note of Windows 1.0 specifically, therefore:
Windows 2.0 allowed windows to overlap, Windows 1.0 could not do this.
Windows 2.0 introduced new and more complex keyboard shortcuts and terminology such as "Minimize" and "Maximize" vs. Window 1.0's "Iconize" and "Zoom"
