As far as i know STO ( Security Offering ) is a type of investment in form of cryptocurrency but is backed by physical and tangible assets like land, building and machineries unlike ICO that is not so tendecy are developer will just lie that funds are already wasted and nothing to spend and will run afterwards.
In addition to what you said. STOs can be crypto currency and may not because what determine that is the concept and strategy planned by the team involve in a certain project but STO are usually token, an asset or utility that project owner usually give it away to their investors during sale as a form of asset.