Runs one step and stops again, reporting where — or null if the page did not stop.

into enters the next call, over runs it without entering, out runs until the current frame returns: step, next and finish as every debugger since gdb has named them.

Stepping is also the only way INTO another frame from here. A debugger statement inside something you call at a breakpoint does nothing, because V8 disables breakpoints for the duration of a debugger evaluation — nothing this REPL can turn on.