What is a baritone?
The baritone is the most common male voice type. Though it's common, baritone is far from ordinary. On the contrary, the weight and power of this voice type gives a very strong sound.
In opera the baritone is often used in roles of generals and noblemen. The most famous baritone characters include Don Giovanni, Rigoletto and Nabucco, all from operas with the same names and Figaro from The Marriage of Figaro.
In a choir, a baritone will never learn about the particulars of his voice since the voice type sings either with the tenors or the basses.
If you sing tenor and can't reach the higher notes with ease, or sing bass and can't reach the lower notes naturally, you're most probably a baritone and you shouldn't worry about it. Let the other singers in your section help out.