1. You will learn some of the language.
..Even if you never imagined you'd be speaking French to the locals
2. You will see incredible things.
Whether you go with a school program our an outside program, during your time outside of school you have the freedom to explore the town and take trips outside the country on weekends, where you will see the most incredible things.
3. You will learn more than you could have imagined.
Aside from picking up enough words of the language, you'll be exposed to some interesting things, you'll have experiences you never dreamed of, and you'll learn from them.
4. You will make some of the best friends of your life.
Whether you're spending just a summer together or an entire semester, or even a year! Over time, you'll become each others support systems. For the good times, and the bad.
5. Sometimes it's good to get away.
Everybody needs a break sometimes, whether you think so or not. Sometimes it's helpful mentally (and maybe even physically) to go somewhere else for a little while -- plus you'll get in a little school too ;)