I read data on real estate industry and there is a table titled "establishments". The title of it is "number of establishments in real estate for all establishment sizes". Is 'establishment' a terminology for real estate industry? Does 'establishment' here means construction sites? Thank you.
Establishments are business locations (source). The real estate industry does not include construction (under either NAICS or SIC). It’s not really possible to tell what exactly would be included without more detail on the specific industry group you are looking at; it could be anything from realtors’ offices to apartment rental buildings, or both+other types of establishments. A summary of the NAICS groups can be found here.