Generic terms for this setup are:
Investment-Only Retirement Account
Non-Custodial Plan
Vanguard does a better job of explaining how this account is set up:
"The Vanguard investment-only program is designed for employers who have a retirement plan with another firm and want to offer their employees a wide range of competitive, no-load Vanguard investments. Your employees can invest in Vanguard funds while your plan administrator continues to serve as trustee and provides recordkeeping."
natb: Your employer should have another company that serves as the plan administrator: ADP, American Funds, Employee Fiduciary, maybe Charles Schwab, but I would guess it's a lesser known administrator. This administrator should provide periodic balance statements, a website to see your account and choose investments, etc. Your HR person seems to have decided the administrator's investment options are bad, and contracted with Fidelity to provide certain Fidelity funds in this account for you to select.