Here you can see what was first started; placing of the pins.
What pins are is just lowering the basement, giving more space and more height.
The problem with older homes is that the basement was never meant to be a living space. It was intended for storage, utilities, laundry, and a nice dark and damp home for spiders to creep about. The height of the basement is often lower than the rest of the floors, coupled with the fact that duct work and utility pipes are usually run along the ceiling area.
Creating a full height basement is not an easy job. To lower your basement, you’ll need to underpin the foundation so that your house doesn’t fall over. Underpinning involves excavating and pouring new footings to the depth where your new basement floor will be. This is done in sections (as you can see in the video, they did 10), and the load of the foundation is carefully transferred and supported as each section is completed. It’s a slow and careful process as you’re basically undermining the integrity of the foundation during the basement lowering process. The basement footprint remains the same but you get the extra headroom.