Brake lines carry brake fluid from the master cylinder to the brakes.
They are basically the same on all brake systems. For most of their length they are steel, coated to reduce the possibility of corrosion, and attached to the body with clips or brackets to prevent damage from vibration. In some vehicles, the brake lines are inside the vehicle to protect them better from corrosion.
The brake lines must be able to transmit considerable hydraulic pressure, so they are mostly made of steel, rather than of a softer but less corrosive and easier to fit material such as copper. However, a flexible section must be included between the body and suspension to allow for steering and suspension movement. These flexible hoses are made of tough reinforced tubing, to contain the pressures as well as to protect them from objects that could be thrown by the tires.
If a brake line is damaged, it is usually replaced rather than repaired.