What are “short URL’s” and how do I make one?

A URL shortener can make it easier to share and communicate a long URL to people, e.g. when you are sharing a download link to your mobile app.  For instance https://itunes.apple.com/app/union-county-nj-votes/id918869362 is shortened by http://goo.gl to be http://goo.gl/nX8Mwr

There are a range of URL shortener services available, e.g. http://goo.gl, http://bit.ly.  Bit.ly provides statistics data on your URL which may be of interest.