It goes beyond the simple action of 'turning on' to indicate that a state is 'in progress' or 'activated.' It's useful for showing that things are going according to plan, like "The project is still on."

Among the younger generation in English-speaking countries, it's used with various ambiguous meanings, such as signaling the start of a challenge or competition like "Game on!" or implying the beginning of a relationship with "We are on!" It can be used wittily to convey positive and vibrant energy.