Rest

Rest is a civ resource requited by all (non-animal) units. It is typically provided by a village via its dwellings.

To support units which must venture far from any civ village, camps can be constructed to supply rest. These buildings are temporary in nature and their quality will fall rapidly. The rest quality supplied by camps is generally much lower than that supplied by villages. More nomadic civilizations may construct wagon trains, slow-moving and vulnerable units which also supply rest.

Rest is supplied in limited quantities by each dwelling, so a civ with a large population will require more numerous dwellings. It is considered a resource and follows the same supply line logic as other resources such that it can be transported over roads or via water to the units which need it (see abstraction for explanation).

Each unit requires access to one rest unit per week. As with other resources, low-quality rest will reduce the overall quality of the unit, and with no access to rest a unit's quality will fall (as their morale suffers from having to remain constantly out in the field).

Abstraction
Rest represents not just sleep, but a break from work and the chance to relax at home with friends and family.

A rest supply line actually represents individuals from the unit returning, along the route indicated, back to their dwelling to rest between shifts. This does not affect the overall strength of the unit because it occurs only during non-working hours not depicted by gameplay—specifically at night, which is not represented in-game since (in this age) people did not generally work, fight, or explore after dark.