Security Tokens and Security Tokens Offering.
A security token offering (STO) / tokenized IPO is a type of public offering in which tokenized digital securities, known as security tokens, are sold in security token exchanges. Tokens can be used to trade real financial assets such as equities and fixed income, and use a blockchain virtual ledger system to store and validate token transactions.
A security token is essentially a digital form of traditional securities. There are three primary types of traditional securities: equities, debt and a hybrid of debt and equity. Examples of securities include stocks, bonds, ETFs, options and futures. Hypothetically, any of these things can be tokenized to become a security token. It is possible that in the near future, security tokens could serve as a very viable alternative and competitor to stocks and other traditional securities.

Investing; ICO or STO
Investing in an ICO won't result in you having an ownership stake of the company you're giving money to. You're gambling that the currently worthless currency you pay for now will increase in worth later and make you money.

Entrepreneurs looking to launch a new cryptocurrency can do it through an initial coin offering (ICO), a variation on an initial public offering (IPO).
There is little to no government regulation of ICOs currently, and anyone can launch one, provided they get the technology put in place.
At the same time, an STO offers the following advantages:
Investors acquire underlying assets that derive their value from something else.
100% regulated offerings that guarantee the security of investors.
Projects aimed at STOs are generally more mature and trustworthy than those in the ICO sector.
STOs are growing significantly while ICOs are shrinking space.
It is a continuing trend.
Securities tokens are expected to be traded through broker-dealers, which are also monitored by regulators.
Security tokens are the next big step in the traditional financial world.
Less speculation and market manipulation.