MDM is correct.
One fun thing to add... I believe that all SIMPLE-IRAs support in service distributions. That means that if you have a reason to prefer the assets are elsewhere, you can transfer out without leaving employment which is typically required by 401ks. I think you may be required to keep the money there for 1 year but that's it. I had a SIMPLE-IRAs for 19 years before stumbling into that. Useful if you prefer vanguard, want a nice $900-$1000 brokerage bonus from Merrill edge with free trades, etc.
One downside is that it's treated as a typical ira for things for things like a backdoor Roth IRA conversion despite the fact that it's employer sponsored with higher limits and matching which would make it a lot more like a 401k, 403b.