An engineered floor board is most often a product combined of 3 materials; A wooden top layer, a lamella core and a backing layer.
A solid wooden floor is, as the name indicates, a floor board made of 100 % solid wood.
There are many differences between these 2 types of flooring, but one of them is the fact that a solid wooden floor can be sanded multiple times - opposite an engineered floor - and therefor a long lasting solution.