If you fail to pay your taxes for a certain amount of time and the amount owed reaches a high enough sum, the IRS may file a Federal Tax Lien on your property as a type of security against your tax debt. If this happens, you will receive a Notice and Demand for Payment with a bill stating the amount you owe. Once you receive that, you have ten days to fully pay the debt before the IRS penalties escalate into a lien.
The Federal Tax Lien basically means that all of your property, including your house and your vehicle, and any rights you have regarding that property is forfeit to the IRS if you do not pay your debt.
Even if you pay your tax debt, having a lien filed in general lowers your credit score and can affect your ability to secure loans for homes or cars in the future. If you are notified that a lien has been filed, you should consider seeking tax help or hiring a tax lawyer to help find a way out of the situation.