A cash game is one where you play with your currency you enter with and not notional chips (as with a tournament). So ring games and fast poker games are all "Cash Games". You buy in with the currency of the table and you cash out in that currency.
In contrast with a tournament you will buyin with a currency, play with tournament chips (which have no direct relationship to the currency you bought in with) and you, hopefully, win a prize based on the currency you bought in with or alternatively a ticket.