A levy is a legal seizure of your property to satisfy a tax debt. Levies are different from liens. A lien is a legal claim against your property to secure payment of your tax debt, while a levy actually takes the property to satisfy the tax debt.
A federal tax lien comes into being when the IRS assesses a tax against you and sends you a bill that you neglect or refuse to pay it. The IRS files a public document, the Notice of Federal Tax Lien, to alert creditors that the government has a legal right to your property. You have the right to appeal if the IRS advises you of the intent to file a Notice of Federal Tax Lien. Your appeal rights are explained in IRS Publication 1660, Collection Appeal Rights (PDF).
When filed, the Notice of Federal Tax Lien is a public document that alerts other creditors that the IRS is asserting a secured claim against your assets. Credit reporting agencies may find the Notice of Federal Tax Lien and include it in your credit report. An IRS levy is not a public record and should not affect your credit report.
To learn more about liens see Understanding a Federal Tax Lien.