The Yak-3 was a smaller, lighter version of the Yak-1. It was an outstanding performer and outclassed all comers at low level. It confusingly did not appear in service until AFTER the Yak-9. The VVS always had a penchant for confusing aircraft designations, but the Yak family seems to have been more muddled than most, becoming more and more screwy until everyone just gave up trying to figure it all out and started building Migs instead.
Cool stuff for Yak lovers:
Check out the Yak-3 T-shirt in the gift shop!