"At the end of the day most of them are either LLCs or C or S Corps."

LLC = Limited Liability Corporation. Files taxes using Schedule "C" like a sole proprietor or another Corporation ("conglomerate" or otherwise). It's a business structure which has officers and titles, and may have other employees. Limited liability in that individuals may still be held personally liable for business activity, but business is typically done in the name of the entity vs. individual.

"C" - Schedule C used to file tax returns. Used by Corporations and sole proprietors alike

Subchapter S or S-Corp - enjoys the corporate business structure for a small entity, can grant/sell stock with ownership rights like "C"s, enjoys individual lawsuit protection for individual assets which are not held in the name of the company, can make matching contributions to 401(k)'s up to 25% of total payroll. Earnings realized as distributions to individual stockholders which are taxed at individual rates, not "C" Corporate rates. A great wealth preservation and building strategy if incorporated in a state where there is no State income or State Corporation tax (e.g., Nevada).

My S-Corp is a Nevada corp., though I do not live in Nevada (perfectly legal).