Why does my bike left gear shift have more than 3 combinations? I just bought a new bicycle and I just read and watched some videos of how mountain bike gears work.

I noticed that the bike is a triple but the left gear shifter has more combinations than 3 (like the ones I saw in the videos). If I am not mistaken, there are the same amount of combinations as there are on the right gear shifter (something like 8).

Can someone explain how this works?

Thanks.
Sounds like a friction front gripshifter with a "Micro-Adjust" shifter.  As mentioned in the comments, that will let you "trim" the shifting a bit.  As you change gears in the rear gears, the chain moves a little side to side, and may rub the front derailleur.  That shifter lets you move the front derailleur cage a little bit to alleviate that chain rub.