Solid hardwood is a plank milled from a single piece of wood. Every board is the same material top to bottom. Solid can be refinished five, six, seven times over its life. It wants a dry, stable subfloor, above grade, usually nailed to plywood.
Engineered hardwood is a real wood veneer on top of a plywood core. The top layer is the same species you’d get in solid, but the plywood base handles moisture better. Engineered installs over concrete, in basements, and on slabs where solid won’t hold up.
Most Montgomery County homes have solid oak on the main floor and engineered (or LVP) in the basement. When you’re replacing a whole house, we pair solid on the main and second floor with engineered below grade.