The telephone network starts in your house. A pair of copper wires runs from a box at the road to a box (often called an entrance bridge) at your house. From there, the pair of wires is connected to each phone jack in your house (usually using red and green wires). If your house has two phone lines, then two separate pairs of copper wires run from the road to your house. The second pair is usually colored yellow and black inside your house. (See What do the little boxes that the phone company has around our neighborhood do? for a description of the telephone boxes and wires that you see by the road.)
Along the road runs a thick cable packed with 100 or more copper pairs. Depending on where you are located, this thick cable will run directly to the phone company's switch in your area or it will run to a box about the size of a refrigerator that acts as a digital concentrator.