Short answer: A traditional HRA reimburses eligible out-of-pocket medical costs; deductibles, copays, and coinsurance, and, depending on the employer’s design, other IRS-qualified medical expenses for employees enrolled in the group plan.
A traditional (integrated) HRA is employer-funded and pairs with the group health plan. Employers decide which qualified expenses it reimburses; most commonly the plan’s out-of-pocket costs like deductibles, copays, and coinsurance, and sometimes a broader list of IRS-qualified medical expenses (Publication 502). The employer owns the funds, sets any rollover, and unused amounts generally stay with the employer. It can’t reimburse individual-market premiums (that’s an ICHRA/QSEHRA function).