What the term "bars" means when buying an espresso machine?

Question

I want to buy a good espresso machine. In some advertissments I see they say "15 bars" for exemple. How many bars the machine should be, so it will make a good quality espresso?

Answer 1

How much pressure is used.

Answer 2

Mainly because in Italy you go to an Espresso bar, meaning the counter unlike the ones in the US and and Canada were you order they pour or make the coffee for you it is more like a restaurant were you order and they either call you or bring it to you, and most place also double in non-espresso hours to a bar or restaurant, as cappacino is a morning drink and espresso is something you have after 11 am