Why correlation used here?

Code:

function letter=readL(image)

load NewTemplates;

image=imresize(image,[42 24]);

comp = [];

for n=1:length(NewTemplates)

sem=corr2(NewTemplates{1,n},image)

comp=[comp sem];

end

vd=find(comp==max(comp));

Code for NewTemplate

letter=[A Afill B Bfill C D Dfill E F G H I J K L M N O Ofill P Pfill Q Qfill R Rfill S T U V W X Y Z]

number=[one two three four fourfill five six sixfill sixfill2 seven eight eightfill nine ninefill ninefill2 zero zerofill]

character=[letter number];

NewTemplates=mat2cell(character,42,[24 24 24 24 24 24 24 24 ...

24 24 24 24 24 24 24 ...

24 24 24 24 24 24 24 ...

24 24 24 24 24 24 24 ...

24 24 24 24 24 24 24 ...

24 24 24 24 24 24 24 ...

24 24 24 24 24 24 24]);

save ('NewTemplates','NewTemplates')

Problem:

i want to know why correlation is used here. i copied the code from somewhere else. But, i didn't find out what is this corelation actually doing. what value comes in NewTemplates{1,n}.

i make number plate recognition and extraction using matlab. In this project i used this correlation.

Please try to give answer.