EIN stands for Employment Identification Number and is also known as a Federal Tax ID number. It is a 9 digit number that should be applied for via the IRS when first starting a business. An EIN is is used to identify a business entity, trust, estate, and various other entity types. All businesses in general need a EIN, according to the IRS. An EIN is required for licensing and permitting as well as opening a business bank account. 
 
You will need an EIN if any of the following apply:
You operate as a Partnership, LLC, Corporation, or as a Sole Proprietor
You have employees
Withhold employee taxes from wages paid to non-residential aliens.
File Taxation forms such as: Excise, sales, employment, or Alcohol Tobacco & Firearms.
Have a tax-deferred pension plan, or KEOGH