Difference of property types

House: 

• This is a stand-alone residence where the buyer is purchasing the house and the land on an individual title.
• Duplexes also fall into the house category, this is because, although they can share a connecting wall, they are usually on separate titles. (I think this is also called Villa)

Townhouse:

• A townhouse is a multi-level dwelling that imitates a stand-alone house. However, a townhouse is usually owned on a strata title.
• This means that you own the residence but you will share the land with neighbours. 

Unit:

• A unit is a stand alone dwelling, or may share a common wall, not usually in multi story complexes etc.
• A unit may or not share of common space.

Apartment:

• An apartment is a self-contained unit that is part of a bigger building that contains other similar apartments.
• If you decide to own an apartment, you will be on a strata title. 
• This means the apartment belongs to you but the common property and grounds are shared with the other owners in the building.