It is perennial, which means it comes back every year. This plant needs full sun and is susceptible to powdery mildew. So you should sprinkle is with sulfur powder in May or June. However, it is technically a short-lived perennial. So if you but a couple inches of mulch over the roots of the plant in late fall your snapdragon may come back again in the spring.
Snapdragons come in three different sizes.
The largest can get as tall as 3 feet. The most common size gets to be about 18 inches tall. The smallest gets only between 8 and 12 inches tall. This dwarf form is good in containers and as an edging plant. Snapdragons need full sun.