Template matching in Ocr

i am new to matlab and was looking for some practice stuff from this site ,i just downloaded ocr code and wen through code , most of the code makes sense to me but template matching stuff is a bit tricky for me to understand ,, i have a-z and 0-9 character's array and then that is stored in a .mat file using mat2cell function and in ocr.m its doing all the stuff ,

Now here i am confused about this procedure , can you pleas explain it a bit how these values are stored and how is comparison made for the given image , i did google and try to understand it but there were few paper which i was unable to understand so if someone can help me with it

HOW THESE VALUES ARE STORED IN .MAT FILE AND HOW DO WE COMPARE IT WITH INPUT IMAGE