The term 'Standards' does indeed reference a number of popular songs - mostly in Jazz (I Got Rhythm, Stella By Starlight etc...) that musicians are expected to know. As different genres of music get older and more established then they start to create their own list of 'standards' e.g. a few weeks ago I was at a jam night that featured a lot of Metal players - it was expected that I could play x bt Metallica, and y by Ozzy Osborne etc...
They just tend to be the most popular tunes to play within a given style.