It shows when and where you last entered the United States. Your I-94 number is necessary for various things, including hire paperwork, your driver's license application, your social security number application, your OPT application, and so on. To retrieve your I-94 number, visit the Customs and Border Protection website.
Your I-94 number is 11 digits. If you think you are typing in all the correct information but still cannot retrieve your I-94, see an International Student Advisor. Sometimes your information may be entered incorrectly in the system.