Lead – This is the qualifier for a sales opportunity. Perhaps someone you met at a trade show that might not be a qualified lead, but you want to keep in touch with them.
Opportunity – Once you qualify your leads, you would convert them to an opportunity. For example, a lead that you have spoken to whom has shown interest in your product.
Account – Once you have closed business with that person, you would 'win' the opportunity and convert the person / company to an account.
Adam MacIntosh is the Manager of Client Services with WebSan Solutions Inc, a Microsoft Dynamics Partner firm.