What is the difference between a speaker and an amplifier?

Good evening,

There are two things:
- A speaker is a cabinet equipped with one or more speakers.
- An audio amplifier is an electronic amplifier designed to amplify low-power audio signals.

By default, to sound a space, you need an amplifier connected to the speakers.
However, there are self-amplified speakers that do not require any amplification source.

As for your second question, for an apartment, a 2 x 250W system pushed to the max is likely to get you into trouble with your neighbors.
Moreover, having too much power is not necessary. If no one enjoys the evening because the music is too loud and drowns out conversations, success is not guaranteed.
It is better to opt for a 2 x 100 W system and adjust the volume reasonably, increasing the power a bit when everyone wants to dance.

Hello

an amplifier is used, for example, to connect a CD player to send sound to the speakers

so, you need at least one source (CD player, computer, MP3), an amplifier, and speakers

25 or 50 Watts is already quite enough x)

So, to begin with, we are not here to advise on organizing surprise birthdays and parties. If you want that, you should go to a special site, okay? So it's pointless; we are not professionals in that area, but we do know how to handle the machines. We don't deal with sound systems, so stop opening topics just for fun that have nothing to do with computing but are more related to hi-fi and sound!!!!!! So, on that note, good luck with your crazy party for 50 people.