Opossums are the only marsupials native to North America.  There are several dozen species, often called possums.  The most common is the Virginia opossum.

 

IS A POSSUM AND AN OPOSSUM THE SAME THING?

Yes, and no.  In North America the opossum is often referred to the colloquially as "possum", similar to the way people refer to alligators as gators, but it's actual name is opossum.  There is an actual animal called possum that is indigenous to Australia and is quite different.

I SAW AN OPOSSUM OUT DURING THE DAY.  DOES THAT MEAN IT'S SICK?

While opossums are nocturnal animals, it isn't unusual to see them out during the day.  In cold weather, food is scarce, or they have been disturbed from their sleeping area, they will venture out in the daylight.

DO OPOSSUMS GET RABIES?

Due to their low body temperature, opossums are very resistant to rabies, and it is extremely rare to come across a rabid opossum.