A public benefit corporation is an ordinary Delaware corporation with one extra commitment in its charter: to operate for a specific public benefit as well as for its stockholders' financial interests. Delaware added PBCs to its corporate statute in 2013, in sections 361 to 368.
The charter must name the benefit, which can be broad, such as expanding access to education, or narrow. The board must then manage the company in a way that balances the stockholders' financial interests, the interests of people materially affected by the company's conduct, and the stated benefit (section 365). In an ordinary corporation, directors must ultimately serve stockholder value; in a PBC, they may choose a less profitable path that better serves the stated benefit, and the balancing duty protects that choice as long as it is informed and free of conflicts.
At least every two years a PBC must give its stockholders a statement on how it has promoted its public benefit (section 366). It need not be audited or certified unless the charter says so. A PBC may put "public benefit corporation," "PBC" or "P.B.C." in its name, and if it does not, it must tell investors it is a PBC when it issues stock. An existing corporation can become a PBC, or a PBC can convert back, by amending its charter; since 2020 that needs only the normal stockholder vote rather than a supermajority, and objecting stockholders generally no longer get appraisal rights.
A PBC is a legal structure. A Certified B Corporation is a private certification from the nonprofit B Lab, based on an assessment of the company's practices. A company can be either, both or neither.
Most venture investors will invest in a PBC, and several well-known technology companies are PBCs. Some investors still prefer the simpler duties of an ordinary corporation, and the balancing duty can make an acquisition slightly more complicated. If a public mission is central to what you are building and you want it written into the company's governance, a PBC is a reasonable choice. Corply currently forms ordinary Delaware corporations, not PBCs.