Your home’s wiring consists of romex, BX cable or wiring concealed in conduit. Romex is a brand name for a type of plastic insulated wire. The formal name is NM that means non-metallic sheath. This is suitable for use in dry, protected areas (inside stud walls, on the sides of joists, etc.), that are not subject to mechanical damage or excessive heat.
Bx cable is known as armored cable. Wires are covered by aluminum or steel flexible sheath that is somewhat resistant to damage.
Single strands of conductor wire are pulled through conduit that is the safest method for wiring for durability purposes.
These different types of wiring carry electrical current from the panel to the device being fed. Wiring is sized according to the load demand required. Check the rated required load requirements marked on each device to determine the needed size wire to carry the needed load.