Foreign Tax Credit Carryovers

I am new to Turbotax. My prior tax returns were done by a CPA who I am no longer able to afford.  In the last tax return, it appears I had a Foreign Tax Credit of $6,750.   This is noted in the "Foreign Tax Foreign Tax Credit Carryover Utilization Worksheet". I have a couple of questions: (1) What is the Foreign Tax Credit and how can I use it?; (2) Do Foreign Tax Credit's expire?; (3) If I don't use it for the next year, can I use it in a subsequent year? Thank you!