Hi Rusty,your leader serves one main purpose, to connect the fly to the fly line. But if you were to simply use one level (same diameter) leader from the fly line to the fly, you'd run into a few problems. When you cast, part of the leader's job is to "Turn Over" your fly. In other words, the leader should straighten out, and flip the fly as far away from the tip of the fly line as it can, so you can control the fly, have a tight line to set the hook, and so the fly isn't right next to that thick fly line that might spook the fish.
In order for the leader to turn over the fly, it needs a certain level of stiffness, so its usually thicker. But a thick leader will be either too large to put threw the eyes on smaller flies, and when its in the water beside the fly,the fly won,t float naturally.
Tapered leaders solve this problem by giving you the best of both worlds- a somewhat stiffer butt section fastened to the fly line, and a thinner part down by the fly.
Also lads,(and ladies) all leaders will knot at some stage,just some leaders are easier to un-knot (like mine)

just try keep an eye on your leaders maybe every 10-15 casts and look for knots,if you spot them early they can be untangled easier,use the point of your hook to catch in the knot and pull apart slowly,do this carefully to avoid damaging the leader.
Hope this helps you
David
P.s check the classifieds-fly lines section- 13 leaders £10