what is it exactly?
It is a small terrier that has its origins in fox hunting in England.
Jack Russell Terrier
 is a small terrier that has its origins in fox hunting in England. 
what's the lifespan of a jack russell terrier Thirteen to sixteen years
wiki:19561833
Jack Russell Terrier [SEP] Introduction
The Jack Russell Terrier is a small terrier that has its origins in fox hunting in England. It is principally white-bodied and smooth, rough or broken-coated and can be any colour. The Jack Russell is frequently confused with the Parson Russell terrier (see the American Kennel Club) and the Russell terrier, which is a shorter-legged, stockier variety. (Within the "Fédération Cynologique Internationale", the "Russell terrier" is also known as "Jack Russell terrier".) The term "Jack Russell" is also commonly misapplied to other small tan and white terriers. The Jack Russell is a broad type, with a size range of .