From Halopedia, the Halo wiki
Overlook is a medium-large sized Firefight map. The map is divided into three sections, the barn, the yard, and the enemy drop zone. The yard and the enemy drop zone are divided by a shallow river with a covered bridge and narrow walkway at the edge where the river starts to descend into the canyon. The enemy drop zone is filled with Covenant supply crates and roadblocks and is one of the main sections where the enemies will land. The yard is composed of two parts: the barn's fenced-in courtyard and the center section which extends into the forest. The forest is a small wooded area with numerous rocks and trees and is divided by a small fence from the main section. The main section spans from the river below to the left side of the barn, and has numerous large rocks in the center. To the right is the barn's courtyard, an area filled with crates, hay bales, a hay baler and three sheds. The area also has a large tower which can be accessed with a jetpack and can be used for sniping. The last section, the barn, has two levels: an upper one divided into multiple rooms (the back room which is where the players would enter the barn in the campaign, a middle hallway that leads to the stairs down to the second floor and a smaller room to the right of the hallway that contains a radio and multiple ammo boxes) and a lower room accessed by a stairway from the upper part. The lower floor links to the barn's courtyard and to the center section to the left.
The following are locations on the map that are so named on the player's heads-up display during gameplay: