Male pigs are boars
Female pigs are sows (gilts when young)
Baby pigs are piglets
The act of giving birth is referred to as farrowing.
Pigs are even-toed ungulates with 4 hoofed toes on each foot, placing them in the Order Artiodactyla (along with deer, hippos, cattle, giraffes, llamas, etc.).
Pigs are known to be highly intelligent and trainable. They can, however, be aggressive, and human injuries due to pigs are fairly common (pigs have 44 teeth, and they will use them).
Pigs have been successfully trained as "truffle hogs," sniffing out and digging up truffles (in case you didn't know, a truffle is a certain kind of mushroom).
Pigs are very prone to hyperthermia.
Domestic pigs typically weight 110 to over 700 pounds (some even up to 1000), though most are sent to market between 220 and 400 pounds.
Vietnamese pot-bellied pigs are commonly kept as pets (George Clooney had one for 18 years). They can weigh between 60 and 110 pounds, though some are considerably larger. They are prone to obesity. Their life expectancy is 12 to 20 years. They can be house trained.
Now there are also "miniature" and "teacup" pigs, but while they might be small for a pig, they will still likely grow to be relatively large compared to other pets.
Photo credit: http://www.cosmosmagazine.com/news/pig-lung-works-with-human-blood/