Difference Between A "Multi Family" and "Townhomes"

[Blake Reynolds]

I have been wondering for a while what distinguishes the differences between these two things?

I often see townhomes where there are only 2 or 4 units all attached in one "building" but when you look them up they are categorized as townhomes and priced individually. What makes that different from a multi family property with 2-4 units that would be considered as a duplex etc. and priced as one unit.