What is the difference between pre-fabricated,...

Custom: Built from scratch to your exact specifications. No standard sizes – you can plan any kitchen, any cabinet style and color; they can fit any unusual nook or ceiling height. These cabinets involve higher costs and longer lead times.
Semi-Custom: Built in standard cabinet sizes but with a wide variety of door styles, finishes, and interior organizational features. A great balance of quality and value. Most popular in LA in the past 15 years.
Pre-Fabricated: Low quality, limited selection, shelf product.