EITC is a tax credit for people who work(ed) and didn't make much money. If you meet the requirements for EITC, and the EITC exceeds the amount of taxes owed, it results in a tax refund to those who claim and qualify for the credit.
ITIN is a tax processing number that became available July 1, 1996, for certain nonresident and resident aliens, their spouse and dependents. The ITIN is only available to individuals who cannot get a social security number (SSN).
You should itemize deductions if your total deductions are more than the standard deductions amount. Also, you should itemize if you do not qualify for the standard deduction.