Originally Posted by Luke1511
What is the difference. Layman terms please. Thanks.
The difference is, if you walk into a bicycle shop, and ask them to tighten the spokes, they will likely ask you, how much? If you ask them to tension the wheel, then they will likely know you want the optimum tension. The proper thing, if your asking a local bike shop (LBS) to work on your bicycle is to ask them to tension and true the wheels, as these two activities always go together.
In many ways the process is like tuning a Violin or a Guitar, there is an optimum amount of tension on a Violin string, just as there is on a bicycle spoke, and it may in fact be different for every spoke on the wheel, to keep the wheel true (completely round, and not moving side to side). Although if there is a huge difference, between the spoke tension on one area of the wheel and another on the same side, then it could be that the rim is out of round. If a spoke is not tense enough, then it is more likely to break, if it's too tense, then it could pull through the rim, destroying the rim. There is some latitude though, each spoke on a wheel could have slightly different tension, but still be tense enough to not break, but no too tense to pull through.
If you get a new wheel, it should be tensioned and trued when new, by the bike shop selling it to you, some will do it as matter of course, some will do it if you ask nicely, and some will charge extra for it. If they say, don't worry about it, ask them point blank if they did it, or not. If they didn't, then ask them to, if they don't want to, then walk out, this should all happen before they see your money. After 100 miles or 160km, the wheel should be checked to make sure it's still true, and proper tension.
A good check, you can do yourself, is to pluck each spoke, it will sing, side by side spokes on the same side of the wheel should sing a similar note, it may not be identical, but should be similar, your checking for spokes that sing quite different notes, also spin the wheel, looking from the side, it should show as round, you can use the side of the brake as a guide, if the rim hops at one point, then your wheel isn't true, second check is looking from the back of the bike, apply the brake until it not quite touches, spin the wheel again, if it touches at one or more points, then it's also not true. The wheel should then be re-tensioned and re-trued.