Explanation
In the example shown, we want to "mark" or "flag" records where the color is either red OR green AND the quantity is greater than 10. The core of the formula is the logical test inside the IF function, which looks like this:
AND(OR(B5="red",B5="green"),C5>10)
Note that the OR function appears inside the AND function. In other words, the OR function is logical1 inside the AND function while C5>10 is logical2. This snippet will return TRUE only when the color in B5 is either "red" OR "green" AND the quantity in C5 is greater than 10.
The IF function then simply catches the result of the above snippet and returns "x" when the result is TRUE and an empty string "" (nothing) when the result is false.
Note: if we didn't supply an empty string, the formula would return FALSE whenever the logical test returned FALSE.
