From a CFO / Manager's perspective, what are the unique characteristics of a perfectly competitive market structure compared to the other market structures (monopolistic competition, oligopoly, duopoly and monopoly) discussed on-line class ?

How do firms make supply / output and profit decisions and how are production levels, prices, profits determined in the various market structures ? In your summary, are certain market participants (consumers & producers) "included" and / or "excluded" in the market process ?