What is the Divisibility and the Division Algorithm
A nonzero b divides a if a = mb for some m, where a, b, and m are integers. b divides a if there is no remainder on division
What is the division algorithm?

What is the euclidean algorithm used for?
determing the greates common divisor of two positive integers
GCD EX)
GCD of 252 and 105 (252 = 21 × 12 and 105 = 21 × 5), and the same number 21 is also the GCD of 105 and 147 = 252 − 105
What is modular arithmetic?
A system of arithmetic for integers, where numbers “wrap around” upon reaching a certain value
What is a prime number?
can be divided evenly only by 1, or itself