Help with Nested IF statements

I need help to understand the following nested IF statement.  I've read a book and online Microsoft documentation and I'm not getting something.    I understand that 1) how the nested IF statement is (logic statement, result if true, result if false), 2) statements can be written in different ways 3) I tried to use my limited knowledge of IF-THEN statements 3)  I tried using the Excel "Insert Function" tool to help me and it doesn't help me understand.   The following formula works and is supposed to make SharePoint columns required under certain conditions:  

=IF([Audit Type]="P-Proposal",IF([Business Review needed?]<>,"", TRUE,FALSE),TRUE)=IF([Business Review needed?]="Yes",IF([Task Status]<>"",TRUE,FALSE),TRUE)

What is bolded red is where I'm getting stuck.    Thanks in advance if you can help me understand this statement.   

The above is supposed to do this:  If user selects P-Proposal, then Business Needed is required, and if Business Review is selected then Task Status is required.