https://www.youtube.com/watch?v=v4cd1O4zkGw

Big O: how the runtime(operations) scales with respect to some input variables(need to be specifiedvg). 
1. Different steps get added:
    O(a+b)
2. Drop Constants:
    O(2N) -> O(N)
3. Different inputs -> different variables:
    O(a*b)
4. Drop non-dominante terms:
    O(N^2+N) -> O(N^2)