Power steering contains 4 main components:
1 - Power Steering Hoses
2 - Power Steering Pump
3 - Power Steering Reservoir
4 - Power Steering Rack
A leak in the power steering can come from any or all of the 4 parts.
Steering rack is connected to the front wheels via Tie Rods. Tie Rods are short metal bars that allow a limited amount of movement and are attached to the end of the steering rack. You cannot see where they are connected to the steering rack as they are usually covered by a rubber flexible dust cover. This prevents dirt from getting in and wearing out the seals of the steering rack. If you find oil inside those rubber covers on the steering rack, then the seals at the end of the steering rack have gone bad. Usually the rack gets replaced at this point.
To prevent the pump running low on fluid due to hot or cold conditions, a power steering reservoir contains fluid for the pump. It is common in places where salt is used on the road for these reservoirs to rust out over time. When that happens, holes appear in the reservoir and allow the important fluid to escape. The Reservoir is usually part of the pump.
Pump is usually powered by a belt off of the engine crankshaft. Over time the seals of the pump wear out and eventually leak power steering fluid. This will be seen by a constant need to top off the power steering. Only option is too replace or rebuild the pump.
Hoses connect the pump to the steering rack and over time the hoses can become brittle and start to leak fluid. At that point the hoses need to be replaced.