The IFERROR() function enables you to trap and handle errors in your formulae.
=IFERROR(value,value_if_error)
Cell A1 contains a formula. We want to use the result of the formula that is in A1, however if the result of the formula is an error value (such as #N/A) then we want to return the phrase "Not found". The formula is therefore
=IFERROR(A1,"Not found")
Before this great new formula came along you needed to use the following formula to manage errors in Excel:=IF(ISERROR(Value),value_if_error,value)
Whilst this worked perfectly well you ended up with a long and sometimes difficult to audit formula. Also because of the repetition of the original formula it was inefficient.
A great step forward from Microsoft. The next step for the Microsoft team will be to build the error handler into the original formulae themselves. Fingers crossed...