There are actually 3 types of programs:
Standard Individual
Standard Company (Apple may require you to fax them incorporation papers).
Enterprise (Must have at least 500 employees according to your Dunn & Bradstreet DUNS report, SEC filings, etc.).
The Standard Company allows you to have multiple team members using one program membership. Standard Individual only allows use by one ADC account. Both limited to 100 devices, plus App store distribution of free apps. If, in addition to joining the $99 program, your paid contract is also accepted, you can submit paid apps to the App store.
Enterprise allows you to have an in-house distribution store for over 100 devices registered to the company.