There are many causes to fret buzz, though the biggest cause is Action. Raising the action will lower fret buzz. Since fret buzz is just the strings hitting the frets, raising the action – distance between the fret board and the strings – the strings arc of motion won’t hit the strings. High action means harder playability, the string is harder to push down.
A balance between good playability and no fret buzz can normally be found. It isn’t hard to adjust action, but in some cases it might be better to let a store do it for you. There are many books that cover complete setups for the guitar and are very accurate. Reading one of these and learning to adjust your guitar will help you save money in the end.
The action is adjusted at the nut and the bridge, not the truss rod – if you’re not sure what this is, it isn’t entirely important. Electric guitars can be easily adjusted in terms of action, both raising and lowering it. However, raising action on acoustics can be a problem since you will need to replace the nut/saddle (the bridge part the strings pass through).
Besides action, which is the main culprit and should be checked first, you can check out a list of causes at Frets.com. You might want to check with the forum to make sure the diagnosis is correct.
Though it is highly related to the acoustic guitar, it still partially relates to the electric.