Fences are the initial enclosures available to the player, allowing segmentation of areas and fields, protecting them from both hostile and plant-hungry wildlife as well as raiding parties.
Fence Gates or higher-tier equivalents are required for fences to be passable by villagers and cattle in the case of a complete fencing enclosure without gaps.
Basic Strategy
While largely decorative and affording limited protection against hostile wildlife and raiders, fences are a great line of defense to prevent deer from consuming crops. Encircling fields and providing access via fence gates will limit this loss of crops to grazing wildlife.
Fences can also be managed via the Wall tool (hotkey: X), allowing for speedy deletion of stretches in the case that field expansions are needed.
NOTE: Deer will continue to spawn at or near their corresponding wildlife resource node, fences will not prevent spawning if the node is near or within fencing perimeters.