Yeah, I had a skin on FM 14 that included the instant result button. I had the skin for so long I actually thought the instant result was an FM feature... was kinda disappointed when I discovered it wasn't.
Anyway, instant result gives you just that, instant result. It basically sims the match without you playing it. If it works like the one I'm familiar with, it gives you options (game plan) like "leave it late", "pressure cooker", "smash and grab" (personal favourite), "go for a big win", "settle for a draw" etc. You can also choose not to use a game plan, and simply sim the game normally. Either way, it saves a loooot of time during long-term saves. I ended up using it very often, especially in unimportant cup games and in league games I should be winning.