A person that speaks two languages is bilingual. A person that speaks one language...
This is an old joke. What do you call a person that speaks one language? American! If you grow up in the United States, there's a good chance your experience with learning a second language (other than English) wasn't a pleasant one. There are probably dozens of reasons why. You hear responses like, "Everyone speaks English," "I don't have a chance to interact with people that speak a different language." "Learning a second language is hard!"
These responses have some truth to them, but when I first began to study Spanish in Mexico while I was in college, it was a great experience! Learning a second language can open up a whole new world for you. You can actually see things in a slightly different perspective, and that helps you get along better with all types of people. You can make a lot more friends if you speak more than one language, for obvious reasons.
But on the practical side, think about what you learn in school that will be helpful in terms of getting a job. Did you know that among the top ten search terms that employers key in when they are on a job hunters website like "Monster" is the word "bilingual"? Now if none of the other reasons can convince you that studying a second language has its benefits, that one definitely should.