a wheel can be out of true several different ways. up and down is bad, and harder to adjust. side to side is more common, that can usually be fixed via spoke adjustments. side to side makes the wheel hit the brakes which slows you down.

what Nomad is talking about is tightening up the spokes for equal tension while keeping the wheel straight and true, this will make the wheel stronger so it will stay straight longer.

most any new bike comes with machine assembled wheels that were just quickly put together and shipped. on a higher end bike, the bike shop is more likely to retune and true the wheels as part of the bike assembly, but on a $500 hybrid, they aren't as likely to take the 10 or 15 minutes this takes to do right. also after riding that new wheel for 100 miles or so, the spokes settle in, and any error gets exaggerated, so they should be retrued. generally if this is done right, they'll stay straight for a long time afterwards, unless something catastrophic happens like hitting a curb hard enough to bend the rim, or break a spoke. my back wheel needs this now, it has a couple millimeters of side to side, not bad, but not perfect, I've ridden the bike aobut 220 miles since I bought it and started on my recovery...