I received a 15109 form. In one of the blocks, it asks for a tax form and year. What tax for is it talking about?

Why did you get form 15109?  That is for you to request a tax  deferment of a tax due.  So it would be for your tax return for the year you are requesting.  So do you want to defer your current tax due for 2021 tax return form 1040?  

I was in a combat zone last year. I'm not entirely sure I need to submit this form, honestly.