Bob did a fine job of explaining the basics of the Game. I have known more than a few players who have been playing and watching Snooker for decades and are still rather fuzzy on some of the Rules so don't feel bad. A couple resources for you:
First, a well put together video from SnookerCanada:
https://www.youtube.com/watch?v=PwSGdl_JgNg
Or if you prefer the written word, Canadian professional referee Jim Jack has a fine write up here:
http://www.rulesofsnooker.com/snooker-for-beginners.html
A couple follow up points to your original post:
Snooker does have a number of variations, mostly used in casual, social play (though there is the odd "alternate rules" professional tournament), but they are all subservient to the main Game as described by Bob.
You can think of the "frames" of Snooker the same as the games of the World Series....each frame is really only worth one "point" whether you win the frame by a score of 72 to 71 or you win it by a score of 100-0. Just like you need four wins to take the World Series, you need the majority of frames to win a match. (Number of frames in any particular match depends on the tournament and the stage of the tournament with the World Championship currently having the longest final match at the Best of 35 frames.)
As long as there are two or more balls on the table, then the losing player is entitled to continue play. There is no such thing as a forced concession. Bob is correct that it is generally common courtesy to concede a frame for expediency when several snookers are required, especially in casual and social play. Professionally, there is no shortage of examples of a player requiring 4 snookers and yet winning the frame in the end. It happens, but not often.
The frame is "officially" finished in one of two circumstances (beside aforementioned "concession"): 1) If the Black is the only ball left on the table and the difference in scores is greater than seven points, the frame is over...a player is not allowed to play on attempting "snookers" unless at least two balls are on the table. 2) If the Black is the ONLY ball remaining on the table, then the next score or foul ENDS THE FRAME (unless the scores are then exactly equal, in which case there are special rules for a "re-spotted Black"--you can easily look up video for that rare occurence). After that score or foul occurs (whether or not the Black still remains on the table), the player then having the highest point tally is officially the winner of that frame (whether or not he is the one who actually scored or fouled the Black--sidenote: Never, ever call it the 8-ball...its name is the Black and its value is 7. This is perhaps my greatest pet peeve regarding new or uninformed players).
Complete official Rules of Snooker are freely available and can be found here:
http://www.wpbsa.com/wp-content/uploads/2016/03/official-rules-of-the-game.pdf
If you are going to be selling tables, it is good that you are boning up on the Game like this. Any questions, feel free to ask.