The study of exoplanetary systems has rewritten the book on what planetary systems generally are like. Before exoplanets were discovered, astronomers only had our solar system to refer to, so theoretical models all used it as the basic template for all planetary systems. Now, we know of hundreds of exoplanetary systems, and none of them are like ours. Even though most scientists think systems like our own will eventually be found, it is quite clear already that a large fraction of planetary systems bear no resemblance to our solar system. Theoretical models of planetary systems and planet formation now include a great deal more variety than just a decade ago. We now understand that even though the solar system follows all the same laws of nature as every other planetary system, it is a surprisingly special place.