what does 15/10 mean in game

I know 15 is minutes but what does the 10 mean?

bonus seconds you get when your turn starts. so in this case you get 10 bonus seconds.

Thanks

That was Bobby Fischer's idea. adding time after each move.

So every time my (or your) turn starts, I start off with 10 extra seconds? What does that do for the game? 

In my opinion, it may prevent players from losing on time. Adding 10 seconds after each turn makes a lot of difference during endgame, especially when running out of time. 

The point is that players are unlikely to run out of time. A player may blunder because their time is low but they won't lose on time itself. It means that if you are clearly superior you should be able to convert the position into a win.

at the end game time is added wc is invariably more than 10 seconds, how do we track this?

I'm surprised this hasn't been brought up yet in this discussion.

But another reason why +10 seconds are added for each successful move is because if a person is writing their moves down manually. IE: A chess.com official move sheet that one printed to a piece of paper, it will give them ample time to write down the move of one's opponent and their own move as well.

This could come in handy for preparing for an in-person tournament.