Ring Game is a term that designates an ongoing poker game and differentiates it from a tournament. In a tournament you buy in and must stay in until you win or are eliminated. Depending on how many players bought in, a tournament can be short or it can be very long. In a ring game you can buy in at any time and cash out at any time.
For this reason, a Ring Game is sometimes called a Cash Game. The chips you receive represent real money whereas the chips you receive in a tournament are just symbolic. You cannot cash in your chips for money in a tournament. In a ring game, if you buy in for $10 you receive $10 worth of chips. This is important for two reasons. If and when you cash out, you will receive money equal to the value of your chips. Secondly, although you can always buy more chips between hands, you cannot buy more chips in the middle of a hand. This is called playing at table stakes.
There are Ring Games for all the many variations of head-to-head poker. There are also limit, pot limit, and no-limit Ring Games. The minimum buy-in for limit games is usually 10 times the minimum bet. There is normally no maximum buy in. In no-limit games the standard minimum buy-in is 40 times the big blind. There is also a maximum buy-in, usually 100 times the big blind. In games without blinds the house sets the minimum and maximum buy-ins.
Every casino uses the term Ring Game to suit its own purposes, but keep in mind that the term simply means an ongoing game in whichever poker format you wish to play. The game may continue for days with all new players every couple of hours. The game ends only when all players cash out but restarts as soon as two players buy in.
Most casinos give you a time limit so the game moves ahead steadily. You are also given a time bank. This is a reserve of time you may need to tap into when you have a difficult decision to make and need some extra time to think.
When you play online there could be technical problems with your computer or server. The casinos make some allowance when you are accidentally disconnected but they have limits on how long they can wait for you to reconnect. If you live in a place with inconsistent computer service you must take that into account when you play poker online.