Unlike the levy which involves intangible assets such as your bank account, a seizure is the confiscation of physical assets, such as your home or car. Seizures usually happen in aggravated cases when someone ignores many requests by the IRS over a long period of time to pay their outstanding taxes.
A seizure should not be taken lightly. The IRS will ultimately pursue seizure of your physical assets.
When the IRS seizes your assets they want to sell them quickly at auction. They often receive less than half your asset's value, so they will seize everything possible including your home, cars, boats, jewelry, motorcycles, insurance polices, even your retirement funds.