What is tally
Do you mean by tally marks?? that is just a way to count up to five. If you want a very technical defintion, here it is:
Tally marks, or hash marks, are a unary numeral system. They are a form of numeral used for counting. They allow updating written intermediate results without erasing or discarding anything written down. However, because of the length of large numbers, tallies are not commonly used for static text.