The If function basically checks to see if a condition is met and then does
something, if the condition is not met it does soemthing else.

For example lets say that if the number 5 is in cell A1 you want the word
'Five' to appear in your cell, if not you want 'Not Five'

The function would look like this:

=IF(A1=5,"Five", "Not Five")

The 1st part of the function looks at A1 to see if it is a 5, there is a
comma which tells the function to do what comes next, in this case put in the
word Five.  then there is another comma.  If the number is not a 5 it will do
that part of the function.

I'm not sure exactly what you mean by your second question you might be
referring to the autofilter command under data...fileter...auto filter.  That
puts arrows on your headings so you can filter more easily.