New boss doesn't like CSVs because "they don't keep the metadata" and prefers RDA and RDATA. What do they mean by "metadata"?

I have a background in GIS and am just learning data science using programming languages. Specifically, I am focusing on learning Python to complement my bosses knowledge of R (we are a new department and there are just 3 of us).

In my previous research, I always either used ArcGIS coupled with data manipulation of CSVs in Excel for my research. My boss says they don't use CSVs because it doesn't maintain the metadata, and most of their files are .RDA or .RDATA.

I don't use R, and am in the process of moving beyond 'inept Python script kiddie, but I keep finding myself doing a lot of work on CSVs in Excel because it's familiar and easy for me.

When my boss speaks of metadata, what do they mean in this instance? I understand what metadata is, but what metadata is being captured in RDA/RDATA that I am not aware of? I have opened some of their data in Python from a feather file they sent me and see no difference from a CSV.