Game modes are different modes available. There are 3 Different modes. Survival, Creative, and Adventure. Each mode has some way of moving faster than normal. In survival and adventure modes, you can sprint by double tapping the "w" key or whatever you change the forward key to. In creative you can fly by double tapping the spacebar. Do deactivate flying, you double tap spacebar again. I listed some more advantages and disadvantages in the table below.

Game modes Survival Creative Adventure
ID Number 0 1 2
Breaking blocks Takes time and you need the right tools Instant breaking Can only break some blocks if you have a sword
Usage Full out survival Building a structure/map Hunger Games