Truing a wheel -
Tightening a spoke pulls the rim to that side. If your spoke is a driveside spoke, and you tighten it, it will pull the rim that way.
And the opposite happens if you loosen the spoke.
So, if your rim is buckled to the driveside, find the buckle, find the spoke that goes to the non-drive side, and tighten it until the buckle goes away.
There's more to it than that, but that's the gist.