Sims don't have to focus only on work. They should also spend some time on fun. Video gaming skill is perfect for that. This page of The Sims 4 guide contains all the important information about this skill.
Playing video games on a good, expensive computer is one of the easiest and quickest ways of fulfilling Sim's needs of entertainment. When Sim plays video games he also levels up his video gaming skill. He unlocks new games with every level and he can also participate in e-sports tournaments, starting as a beginner, and after level 6 as a professional gamer (you need to pay a small entry fee and you can win some Simoleons).