some time ago a friend made a graph on a sheet for me.

Now he did something that to this day I have been unable to recall or find
any documentation on, I can not even remember what is did in the sheet or
how it worked.

All I know is all the formula did not work until he did this step.

I would imagine this will be easy if you know what it is this if just an
example not the actual code.

The actual code used a number of if statements in it if I remember
correctly.

Now this was the trick

The STD Code would look like this below.
=VLOOKUP(Sheet2!A1,Sheet3!A:E,2,0)


He then pressed two keys wile in the formula and the formula then looked
like this.
Note " at the beginning and the end.
The formula did not work until he pressed the key combination and the
formula was placed inside " ********* ".

"=VLOOKUP(Sheet2!A1,Sheet3!A:E,2,0)"

Can you explain this step and what is was doing.
Where is the documentation to this process in excel I am sure it must have a
name.

Note
Just placing the formula inside " " does not work you have to press this key
combination like ( Eg ctrl,shift,f2 ) this is not the actual key comb,

Thanks for your help.

Rick