I took a very long time to get it as well, I think governments are doing an awful job explaining it.
So cash is physical paper which signifies debt to you backed by the government. Your money on your bank account is backed by your bank. A CBDC would be like a bank account, but directly backed by the govt, so I imagine all fees are paid from your taxes, and I imagine you can pay in a shop with your ID card. The point is that then all cash can go away, the government does not print money by printing it, it does it by increasing a number in a database table, and pays its obligation digitally.
Proponents of it talk of cutting the costs of actually printing money and decreased crime since you can no longer pay people “under the table”.
Opponents of it talk of governments getting complete control over your finances.