What's the difference between a multi-unit and a single-unit property?

When you add a property, Rentingwell asks which kind it is.

• Multi-unit property: divided into units rented separately to different tenants. A duplex, a triplex, a house with a basement apartment, or an apartment building. Add each unit so you can attach its own tenants and lease.
• Single-unit property: rented as one whole, like a condo, a townhouse or a whole house. You don't add units: the tenants and lease belong to the property itself.