Zenonia incorporates a Weight Gauge system, in other words you can only carry a certain amount of items. Usually the amount a character can carry is based of Strength. However, Zenonia has consumable items that permantely increase this as well such as Feather of Oblivion.
It is important to sell off useless items and equipment for both monetary reasons and survival. If you exceed your Weight Gauge your character becomes heavy and moves at a significantly slower speed, making you an easier target to attack. There is no limit to how far above your Weight Gauge can go, meaning you can pick up as many items as you like.