STO stands for Security Token Offerings. In essence, they are similar to an ICO, but also comply with legal requirements. STOs emerged to regulate blockchain-based crowdfunding, to offer greater guarantees in fundraising using tokens issued on a blockchain, and to prevent lack of oversight.

Comparing ICO and STO shows how much more convenient the latter is for investors. It can take a lot of time, money, and effort for fundraisers to get the green light from regulators to initiate their STO, but investors understand that the tokens they receive for their money are something tangible (assets, profit, income, etc.). So, from an investor's point of view, STOs are definitely safer than ICOs.