If Statement in Access - Need Help Understanding

Hello All,

I am new to Access, below are statments used in Access at my job. Can you please help me understand the formulas to the following two numerators and denominators? (where [Fico] is the credit score of sales made)

Example 1
Avg Fico Numerator LT600: Sum(IIf([fico] Between 1 And 599,[fico]))
Avg Fico Denominator LT600: Sum(IIf([fico] Between 1 And 599,1,0))

Example 2
Avg Fico Numerator: FICO
Avg Fico Denominator: Sum(IIf(Not IsNull(tbl_detail.FICO),1,0))

I appreciate your help very much!

Hendrix -