an amp for amplifying AC v an amp for amplifying DC.
Been There was talking about the first situation. In general a DC coupled amp presents no capacitors in the signal path and is therfore capable of amplifying DC. It is also capable of amplifying AC - up to its frequency limit. This does not mean there are no capacitors in the amp - there may be bypass and feedback caps.
The second situation is more complicated as certain types of amps exist which amplify DC by converting it to AC - they are called chopper amps.