Space and Time Complexity aka Big O

What is good code?
Good code should have two different things that it can be described as:

Readable - Can other people understand your code?
Scalable - Big O notation is what allows people to measure if code that is written is scalable

Code is written by programmers, a set of instructions for the machine to use
The machine takes that code (instructions) and runs through it
There is an output based on the code (instructions) that the programmer has written

Cheat Sheets

Big O Cheat Sheet

Sorting Cheat Sheet