Risk-on describes the mood of the market when people are feeling brave. When investors are optimistic — maybe the economy looks healthy, or borrowing money is cheap and easy — they become willing to put their cash into things that can grow quickly but can also fall hard: crypto, technology shares, small young companies.
In this mood, money flows toward risk, chasing bigger rewards. Prices tend to drift upward, and every dip gets snapped up quickly, because plenty of people are eager to get in and are afraid of missing out.
A useful way to picture it is a party in full swing: everyone is confident, spending freely, and the good mood feeds on itself. The music is loud and nobody is thinking about the exit.