How many watts of amplifier do I need?

Hello there, I'm curious about something related to amplifiers. Could you please clarify for me - when someone asks, "How many watts of amplifier do I need?", what exactly are they referring to? I understand watts are a measure of power, but in the context of audio amplifiers, what factors should one consider to determine the appropriate wattage? Is it solely based on the speakers' power handling capabilities, or are there other variables that come into play as well? Your insights would be greatly appreciated!