The truss rod is a machine that adjust the bowing of the guitar neck so that if you fret the first and the last fret there should be a small clearence between the string and the fret in the middle.
The buzzing in your guitar may be a result of a wrong truss rod adjustment.
Search for truss rod adjustment for your guitar , most guitar manufacturers sites got some tech tips on setting it up... If you don't feel you can do it yourself , have a guitar tech to do it for you.