EIN stands for Employer Identification Number and is your permanent number and can be used for most of your business needs (e.g. applying for business licenses, filing taxes when applicable, etc). (money.stackexchange.com)
The difference between sole proprietorships and LLCs is that LLCs may have their own tax ID, which is called Employer Identification Number. (personalmoneyservice.com)
You operate multiple businesses in a state or in more than one state with the same employer identification number (EIN) (healthcare.gov)