It's important to understand the differences so you can properly use the three aspects of Properties in Property Meld.
To locate the three sections, you first have to go to the Properties section.
You will then see the three sections appear near the top of the screen.
Units - are the individual suites, apartments, units, and so on. Often times these are subdivided areas within a larger unit known as the 'property'. All properties have at least one UNIT.
Properties - is the building as a whole. PROPERTIES occupy a single address and can have a single living residence or multiple. PROPERTIES are made up of a single UNIT, or multiple UNITs.
Property Groups - a way to organize your data so that you can filter based pre-set information. For example, if you want to look at 25 properties and put them in a PROPERTY GROUP called 'West Wing', you could filter for 'West Wing' and see only those 25. The PROPERTY GROUP is a custom filter feature that allows the user to group properties and units however they see fit.