In most jurisdictions, a public offering requires the issuing company to publish a prospectus detailing the terms and rights attached to the offered security, as well as information on the company itself and its finances.
Many other regulatory requirements surround any public offering and they vary according to jurisdiction.
The company issues additional securities to the public, adding to those currently being traded.
A public company may also offer and list other securities alongside its shares.
If it is an offering of other securities, this entails the creation or expansion of a series (of bonds, warrants, etc.).
However, more rarely, public offerings take place in the secondary market.