Do the terms “hardwood floor” and “solid wood floor” mean the same thing?

Not exactly - 'Hardwood' refers to the species of tree that the flooring is made from. For example, oak, maple and ash are types of hardwood. This term can be slightly misleading as hardwood is not necessarily harder or more dense than soft wood. Spruce, pine and larch are types of softwood.

The terms come from the fact we refer to deciduous trees which lose their leaves annually as hardwood (these trees grow slowly and as a rule of thumb tend to be more dense).

Solid wood simply refers to the construction of the piece of flooring. You could have solid hardwood (a solid oak floor for example), or a solid softwood floor (pitch pine is an example of a softwood floor would see in Ireland).

An engineered oak floor could be referred to as an engineered hardwood floor.