Symbols in command descriptions represent specific text you type or present options.
a container that HyperCard will get information from. It can be a literal ( 5 or "abc" ), a computed expression
( 45*3+22 ), the contents of a variable*, the contents of a field (field "Total" of card "Accounts"), or the Message box.
a container that HyperCard will put information into. It can be the contents of a variable, the contents of a field (field "Total"), or the Message box (the default with many commands).