The fundamentals of arithmetic are the disciplines of addition (you had some, now you have more: how much do you have in total?), subtraction (you want to give away (or sell) some of what you have: how much will you have left?), multiplication (if a cow bears two calves, and you have twenty cows, how many calves will you get?), and division (you have an amount of money, and three barbarians (who are definitely not Vikings in any way, shape or form) -- how can you split your money up so that everyone is happy, and how many pieces can they break you into if you do not?)
Later, under Arabic influences, concepts such as zero, and fractions were introduced.