In spite of post-apocalypse people must buy necessary things. In the Division you need to do the shopping to get better weapons and gear. You can visit different vendors to buy the equipment you need.
They can be divided into some kinds. The basic vendors will kit you out at the Base of Operation before your first forays. Besides that you are able to find some of them in the Dark Zone. These vendors can offer you some specific equipment. They are into safe buildings. But you should to fulfill various the Dark Zone requirements, kill the enemies and looting to get the special currency to buy weapons, gear, etc.