First, check your owners info for the Traeger as I've heard if ya use any pellet other than theirs it'll void your warranty.... Now, I've never used their pellets but to my understanding they use pellets that have an oil added to them for the flavor, rather than a real wood pellet !
There's a thread on what's in traeger pellets. Basically, in the western US the base wood is alder with 30 % of whatever the flavor wood is; the two exceptions are mesquite and hickory which are 100 percent alder with some flavored wood oil mixed in (alder pellets are 100% alder).
In the East the base wood is oak...