COUNTIFCOUNTIF is good for vacation/business trip planning because it counts any number of the same thing. Say, there is a spreadsheet showing a yearly or monthly calendar where you input letters for every person going on vacation (to avoid everybody disappearing at once). Unfortunately there are only a limited number of holidays one can take, so an extra cell might calculate the number of times you input a V, then Mrs./Mr. V knows that her/his vacation planning has come to an end when that number hits the limit.Another idea could be to count the number of times something reaches more than 100 per cent. With COUNTIF you can count all those cells that show more than 100 per cent  then you might know how many categories of whatever have reached more than planned (you won't know which categories  see IF,AND,OR for that question). 
The COUNTIF function has 2 arguments: COUNTIF(search in this area;how many of these you can find there)
No matter whether COUNTIF looks for letters, words or numbers  the second argument (what countif is supposed to look for) is always put in quotes.

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