What's the difference between paying myself an owner's draw and a salary?

It depends on your entity. As a sole proprietor or single-member LLC, you don't take a salary at all — you take an owner's draw, simply moving money from the business to yourself. The draw isn't a deductible expense and isn't taxed when you take it; you're taxed on the business's total profit regardless of how much you withdraw. As an S-corp owner, it's different: you must run a reasonable salary through payroll (with payroll taxes withheld), and you can take additional profit as distributions, which aren't subject to self-employment tax. So a sole proprietor's "pay" is just a draw against profit already being taxed, while an S-corp owner has both a formal W-2 salary and distributions. Either way, set aside money for taxes from every dollar, since nothing is withheld on draws or distributions.