Your first IF formula
IF takes three things, separated by commas: a test, what to do when the test is true, and what to do when it is false. =IF(B2>=50,"Pass","Fail") reads almost as plain English.
Text inside a formula needs double quotes. Without them Excel looks for something named Pass, finds nothing, and returns #NAME?.
The boundary is where these go wrong. A pass mark of 50 means fifty passes, so the test is >= and not >. One character, and in a real class it is the difference for every student who scored exactly 50.
In C2, write an IF that shows Pass when the score in B2 is 50 or more and Fail when it is not. Then fill C2 down to C7.
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