https://www.codecademy.com/courses/ruby-beginner-en-Zjd2y/0/7?curriculum_id=5059f8619189a5000201fbcb

I didn't get any error, i'm just wondering what does this " require 'prime' " do?

```
require 'prime'
def first_n_primes(n)
# Check for correct input!
"n must be an integer" unless n.is_a? Integer
"n must be greater than 0" if n <= 0
# The Ruby 1.9 Prime class makes the array automatically!
prime = Prime.instance
prime.first n
end
first_n_primes(10)
```