You are typing the argument to a command.
These commands are available here:

Return	Enter the line.
Escape	Fill in the default string, if any, as shown within
	parentheses. Only works at the beginning of the line.
^F	Fill in the current filename.
^G	Abort this.
^Q	Insert the next character. (Quoting ^@ won't work).
^U	Rub out the whole line back to the prompt.
