This is a reel in the key of G.
Reels are the most challenging pieces in the repertoire of the traditional musician because of the need to play them at speed and yet include ornamentation.
A very nice rendition of this is on Martin Hayes self-titled album (accompanied by Randall Bays). Martin's website is www.martinhayes.com - when we checked some of the links were not working, but you can also buy the CD from Green Linnet, or to download from emusic.