If you click on a different verse number in the main passage area a list of references for that verse will be displayed.  You can click on any of the references to display that reference.

At the top of the reference list is the verse that you have selected (or the first verse in the passage you are viewing).  This is from your default Bible version (set in preferences) - this helps you to remember where you are when studying long passages and also provides a handy parallel version if you are looking at a different Bible version in the main passage area.