Co-founder vs Founder vs CEO and Founder: Co-founder = a [founder] when there's more than one person at the origin. They're the same role; co-founder just describes the plurality. [CEO and Founder] is the title combo, a founder who also currently holds the CEO job. Read the founder entry for the origin-role definition; read this entry for the team-dynamics nuance (when does someone "earn" the title, what happens when there are too many, how the title gets misused as a recruiting tool).
A co-founder is a person who shares the work, equity, and financial risk of starting a company from its earliest stage, typically before product-market fit. The title is not granted by paperwork. It is earned by being on the cap table and on the ...