I think - apartment (US English) = flat (UK English) = unit (AUS English) - ‘living quarter’ that shares a floor with others in a building (of several units)

• apartment block (US English) = condominium (US English) = block of flats (UK English) = strata building (common in AUS English) = a building (on a site) that is subdivided into ‘lots’/’apartments’/’flats’/’units’ .

There are issues with ownership, responsibilities, liabilities,… of lots/… and the site/property the build is on.