A debugger command starts with the symbol name of the command, possibly followed by some arguments on the same line.
Some commands prompt for additional input.
The current frame is the frame that commands refer to. The debugger evaluates forms in the lexical environment of the functions being debugged. The debugger can only access variables. You can't go or return-from into a function, and you can't call local functions. See section 3.4 for more information on debugger variable access.