This is the most common approach to correcting deflections in a slab type foundation. These are driven downward into the soil by hydraulic force in order to get past the soil's active zone. The active zone is responsible for the swelling and shrinking that causes foundations to move.
These are a step up from concrete piers in that the starting pieces are the same as the starting pieces of a steel pier. When a specific point of refusal (pressure) is reached with the steel portion of the pier, a transition piece is installed and then the pier is finished off with concrete cylinders.
Steel piers are smaller in diameter than concrete cylinders thus enabling a deeper point of refusal. Most homes do fine with the concrete cylinder or blended pier approach. Some homes, however, are heavier and need deeper penetration and closer pier spacing to achieve positive results.
Pads are used in pier and beam type homes in order to achieve a larger footprint for the home to sit on. Often, bricks are used to support the floors. Concrete pads are 16" by 16" in size whereas two brick sitting side by side only provide 8" by 8" at best. Sometimes, there are not any concrete or masonry supports. There will be wooden pegs attached to every other joist with one or two bricks on the bottom. Wooden pegs are an invitation for termites into the home. Even if the home is level, these wooden pegs need to be removed and replaced with concrete pads to decrease the likelihood of a termite infestation.
Some pier and beams have an outer concrete wall that is suitable for traditional concrete piers. This concrete wall will settle over time if conditions are right. Some homes have a stem wall as opposed to a concrete wall. As long as the stem wall has a decent footing, it can be lifted and stabilized. Homes like this will likely need a mixture of piers, pads and beam to achieve a positive outcome.