Use amplifier as speaker?

I have an amplifier and now wanted to ask if you can use it as a speaker. He has a USB input. Would either connect it to my laptop and play music with it or order me a USB to Aux cable for the phone.

Would that work.

The question is completely nonsensical, how should an amplifier work as a loudspeaker, if that would be possible to amplifiers no speakers are connected.

An amplifier amplifies electrical signals. It is not a 'transducer' that converts electrical signals or vibrations into mechanical vibrations that can then be heard. That's what a speaker does. (The opposite is done by a microphone.)

If the USB socket can be used as audio input, you can connect PC and amplifier. However, the speakers are still missing.