Player characters and their non-playing character (NPC) heroes can only carry so much before they are considered "encumbered" and can no longer move with such heavy loads. At a minimum, humans, elves and dwarves can carry 60 pounds before they are encumbered while halflings can carry 40 pounds. This maximum increases with additional strength, however, according to the chart to the right (below on mobile devices).
Note that a variety of magical spells and effects (such as the first level magic-user spell Floating Disk) can increase an individual's carrying capacity.