When you reach 1 billion for the first time you will get your first skill point. Skill points are activated manually and when done so will grant you special bonuses. The first skill point you get is the 'Speed Upgrade' which makes all your workers work three times faster than what they normally do for 30 seconds. These special bonuses come with a cooldown period but can be used whenever they are available.
Top Tip: Combine skill points when you have an advert campaign active for maximum profits.