If a health insurer or a state-run agency pays the medical bills related to your accident, they are entitled to reimbursement.
If you eventually receive a personal injury settlement or a favorable court verdict against the defendant, they will be reimbursed for what they paid.
So, for example, let's say you receive a settlement of $10,000.
If your insurance company paid $4,000 for your medical bills, they would be reimbursed that $4,000 from your settlement, leaving you with $6,000.