That’s the menu to pick characters before you play a match. For Goliath, you start with three skill points, allowing you to distribute your points across three different abilities or completely max out one if you’re confident enough.
For example, if you start by upgrading to a level three rock throw, you’ll inflict a much larger amount of damage compared to a level one rock throw, but you have no melee abilities apart from your standard swipe/claw attack, meaning you will have to stay relatively far away from the hunters to do successful attacks. Hunters could then strategise against this by getting as safely close to you as possible, which would explain why there would be a need to mix abilities.
Once you get to level two, you unlock three more skill points, which again could be distributed or used entirely on one ability. The same rules apply with level three, so in the end you could have three completely maxed out abilities, or a variety of different combinations.
Overall it just helps to give more variety to the gameplay, allowing more strategies to be formed and letting people play “their” way. It was a very good decision to change the skill system to this in my opinion.