The armor system in Fallout 4 is unlike previous games that used a single article of clothing for an entire outfit; instead, different armor pieces for the head, torso, arms and legs can be mixed and matched to create unique combinations. Specialized armor, namely power armor, requires pieces of armor specifically for different body parts, like the left leg or right arm.
Legend
Name: The name of the gear in question; usually what appears on your Pip-Boy.
DT: This is the Damage Threshold of the gear. It is the amount of damage you can expect the armor to absorb before the user suffers hit point loss.
Weight: How heavy the item is, adding to your Carry weight.
Value: How much you can expect to sell the gear for, assuming the merchant is buying your items at 100% of their value.
Health: This is the hit points of the gear when in full condition. It shows how tough it is.