What is the difference between ICO and STO?

Could you please clarify the fundamental distinction between an Initial Coin Offering (ICO) and a Security Token Offering (STO)? I'm particularly interested in understanding how they differ in terms of regulatory oversight, investor protections, and the nature of the tokens being offered. Are there any key benefits or drawbacks that one offers over the other? Furthermore, what impact do these differences have on the overall risk profile and potential returns for investors?