As an adventurer you discover all kinds of interesting items. Some of the items are mundane and others magical. The most obvious items are your weapon and armour. As you advance, your helm, glove, boots and cloak are all replaced by magical items that you have discovered. Eventually a point of saturation is reached and the only way to increase your power level is by gaining the next version of your current item. Advancing your magic weapon from +1 to +2 and so forth.
As your character advances in level wealth continues to accumulate and there is the ability to find or purchase additional magic items. Many of these items are consumables, but are still worth obtaining. I am a fan of items that require healing surges to power them. Especially for those defenders who have more healing surges than they could ever likely spend during the normal course of adventuring.