Content is organized into keys and versions in a spreadsheet. The first column is always the keys, and every other column is a content version. Each row has a content key.
A Content Version is a collection of content. These are columns on a spreadsheet.
A Content Key is a unique identifier of a piece of content. These are rows on a spreadsheet.
A Push transfers content from a design file to a spreadsheet. This will automatically create any missing content keys in the spreadsheet for the design layers that are pushed.
A Pull transfers content from a spreadsheet into a design. The design will be updated with the chosen content version.