The lien can be against you, your spouse, or your company. A lien against your company would seize your accounts receivables. At this point everything you own is just one short step away from becoming the property of the United States Government.
Liens filed against you by the IRS also show up on your credit report and often prevent you from opening a checking account or borrowing against any assets, like your home. The banks don't want the extra work when the IRS comes in to take your money.
With a Federal Tax lien on your record you can't get a reasonable loan to purchase a car. Think about paying 18-22% interest on a car that is already too expensive. You definitely cannot buy or sell any Real Estate. The list is endless.
Levies
Levies can really do a lot of damage and even ruin your life. A levy is the IRS's way of getting your immediate attention. What they are saying is, we have tried to communicate with you but you have ignored us. Levies are used to seize your wages and whatever other assets you have. If you own it, they can take it. That includes checking accounts, auto's, stocks, bonds, boats, paychecks, and even Social Security checks!
Wage Garnishments
You received a notice of "intent to Levy" 30 days ago and you forgot or ignored it. Now it's Payday. Expecting a check, you open the envelope and find that the IRS has taken most of your money. What's left is not enough to pay the rent, car payment, buy groceries, or pay the rest of the bills. This action will continue on every check due you, until the tax owed is paid in full.