It's SIMPLE. It's an Acronym.

It is supposed to be contributed to through payroll. They can't put money into the account directly.

They can also have a regular IRA, of course. But they also are covered by a retirement plan at work, because a SIMPLE IRA is a retirement plan the employer establishes.

So, they didn't manage their own retirement plan for the benefit of their employees, which is themselves?

The employer can make a 2% nonelective contributions up to the tax filing deadline for the business. It's too late to make a matching contribution for 2024 if the employees didn't make voluntary deferrals.

From: https://www.irs.gov/retirement-plans/retirement-plans-faqs-regarding-simple-ira-plans

"Contributions

What types of contributions may be made to a SIMPLE IRA plan?

Each eligible employee may make a salary reduction contribution and the employer must make either a:

• matching contribution or 
• nonelective contribution. 

No other contributions may be made under a SIMPLE IRA plan.

Can contributions made under a SIMPLE IRA plan be made to any type of IRA?

Contributions under a SIMPLE IRA plan may only be made to a SIMPLE IRA, not to any other type of IRA."