The ARC Form itself has help available for every field right on the form. For reference here is each field and the corresponding help text.
Employer or Entity Type
A sole proprietor is person who owns an unincorporated business by themselves and reports business activity on their Form 1040 Schedule C. Sole proprietors are not typically subject to the Employee Retirement Security Act of 1974 (ERISA). Single-member entities can be different from sole proprietorships. If a business has registered with the state in which it operates and the business name includes an LLC or Inc, it is considered a filing group, even if it has no other employees.
An employer benefit plan sponsored directly by a state or local government (e.g., city, county, township or school district) is not typically subject to the Employee Retirement Security Act of 1974 (ERISA).
An employer benefit plan established or maintained by a church or by a convention or association of churches (includes plans sponsored by tax-exempt, church affiliated organizations (e.g., schools and hospitals) is not typically subject to the Employee Retirement Security Act of 1974 (ERISA).
Total Eligible Employees
The number of employees enrolled in the medical plan.
Employees with Qualified Waivers
The number of employees enrolled in COBRA or State Continuation.
Net Eligible Employees
The total number of eligible employees, less any qualified waivers, plus any continuants. (This field is calculated automatically)
Participation and Status
The number of enrolled employees divided by the number of net eligible employees. (This field is calculated automatically)
If the number of full-time equivalent employees in the past calendar year is 20 or more, your company is subject to COBRA; otherwise State Continuation rules apply. (This field is calculated automatically)
Employer Contribution Percentage
This is the percentage of premium paid by the employer.