A chest rig is a piece of tactical gear consisting of multiple pouches that is worn on the upper body to hold various items, such as magazines, walkie-talkie, combat knife, and other useful tools. Typically strapped on using a harness system. It is separate from any clothing article. Intially designed for military and police during combat, chest rig has been adopted for civilian use - especially ones designed with a single pouch.
How to distinguish
☑ post #5400538 depicts a chest rig. Pouches are separate from clothing article, situated on the torso/chest.
☒ post #5374209 depicts a load bearing vest. Pouches are integrated with the tactical vest.
☒ post #5944716 and depict load bearing equipment. Situated around the waist, the gear may consist more than just ammunition pouches.