Ranged weapons are those weapons that can be used to affect creatures in rooms other than the one you are presently in. The most common forms of these are bow & arrows and certain thrown weapon types (daggers, axes). Ranged weapons tend to do decent damage upon impact but the true worth of a ranged weapon is in its ability embed itself in an enemy. The chance of embedding with a ranged weapon is roughly related to the weapon's sharpness and such an embedded weapon can do additional damage if it is extracted in the wrong way (ripped from the body) or if it left embedded for a long time (festering in the wound).
Ranged weapons cannot be used in a peaceful room or against a target in a peaceful room. Also, since some rooms are off-limits to mobs, ranged weapons can not pass through such rooms.
Thrown weapons typically have a short range and low damage, but require no or little training. Bows tend to shoot further and do higher damage. Damage incurred is a function of the weapon's natural damage, the force with which it was launched and how close to the target it was fired from. The best damage would be from a powerful weapon, fired very close to the target using a weapon that could go very far total.
Specialization in ranged weapons will permit increased accuracy as well as the use of more complicated and bigger bows.