tkvars is a manual page for Tk. See https://www.tcl-lang.org/man/tcl8.4/TkCmd/tkvars.htm for details. Tkvars describes Tcl variables that are used or set by Tk. These are (for Tk 8.4):
If the wish shell was called with the '-geometry' option, there will also be a variable 'geometry' defined, and then contains the value given to the '-geometry' option on the command line.