"The country" is an area where there are a lot of farms, forests, and very small towns. You usually compare "the country" to "the city":
I grew up in the country, so it's hard for me to even imagine what it's like to grow up living in the city.
You always have to use "the" when you're talking about "the country". If you don't use "the", people may think that you're talking about a country like The United States, Australia, China, etc.