Solid Hardwood is cut from a single piece of wood with no layers.
Engineered Hardwood is made up from multiple layers consisting of a think top layer of solid hardwood, an inner core of high density material and a hardwood backing.
One important consideration between the two types is that solid hardwood can only be installed above or on grade and is not recommended below grade due to moisture concerns. You will not have the same issue with engineered hardwood and can use it it where moisture may be present.
Both are considered hardwood and provide you with a beautiful timeless look for your home.