An EIN is a federal tax ID number for businesses. You can create one for your business (sole prop, etc.) at the IRS web site. It will be linked to your SSN, so you can use the EIN on your schedule C and your personal SSN on the rest of your tax return and everything will be linked and will not confuse the IRS or mess up your taxes.
An EIN is required if you have employees, but I recommend it for any small business person because it allows you to do business without giving your personal SSN to your vendors and clients.
