Concrete raising, perhaps better known as mud-jacking, is a process for raising concrete in place. Small holes are drilled, and a mud slurry is pumped under a slab, creating pressure, and raising it up.
Uneven concrete can cause negative drainage, which can be very damaging to foundations and stem walls. Also, it can be a tripping hazard or an eyesore.
You know that one uneven seam in your driveway you always forget about when you're shoveling snow? Yeah, the one that makes you hurt yourself with your snow shovel. I'll fix that for you too.