[Discussion] What is a Bar?

Sorry for the stupid question. My musical theory is poor, at best. My playing ability is only marginally better (but improving...)

But I was learning about bars a while ago and was just told:

A bar is a length of time which has a number of beats within 
it.  The time can be any length and the number of beats can 
be any number.

But I never understood then why and what is the point of it?

Is there any difference between a 1 second bar with 4 notes/beats and a 2 second bar with 8 beats?

I can imagine if you scrap them completely then it would be difficult/impossible to play the music at the correct speed if you are coming in blind..

But I guess since I only tend to play music that I already know - I already know how fast it should be so the bars seem meaningless to me. I tend to gloss over the technicalities and just get to playing notes

I always seem to come up with tonnes of questions on music/notes/scales/composing/etc but never really find answers. I might compile a bunch if nooby questions don't bug people too much.

Thanks :)