What does Beer before bong mean?

Beer before bong meaning in Urban Dictionary

"alcohol before bong, that is only wrong"Usually accompanied by "Bong before beer, you're in the clear"This set of phrases is provided as a word of caution to men and women wanting to cross-fade. It is in line with the trend where those who take in alcohol before cigarette smoking weed usually get sicker and puke, whereas those that smoke weed before ingesting cannot.