Ranks are the leveling system used in MCInfected 2.0. As you rank up, you progressively earn better gear and more items. Once you get to Rank 25 or Commander, you have the option to spend 5,000 cookies and prestige. When you prestige, your rank will be reset to Private (Rank 1), your cookies will be reset to 0 and you will given 2 prestige tokens.
The graph below shows the amount of cookies needed to rank up, and how much it costs overall to buy these ranks. In addition, it shows the amount of cookies needed to rank up with the prestige perk Firesale.
(Click the graph to enlarge it)
Your progression of ranks can be viewed by right clicking the stone sword in the MCInfected lobby, whichever block of stained glass is enchanted will be the rank that you have reached so far, this can be used to tell how many ranks you have before you reach the Commander (Rank 25). As you can see below the player has reached rank 2.