Can someone explain how sieve of eratosthenes algorithm works and segmented sieve too?

Question

Sieve of eratosthenes algorithm is used for finding prime numbers with very efficient time complexity.
This is a link to algorithm
http://www.geeksforgeeks.org/sieve-of-eratosthenes/

Answer 1

This algorithm gives you all prime numbers from 2 to determined P.
1) Set all numbers from 2 to P to list.
2) Set current variable n=2 (this is the smallest prime number).
3) Remove from this list all numbers that are multiples of current n.
4) Set new value for variable n: next number of updated list after current n.
5) Repeat operations #3 and then #4.
Finally you'll get a list with only prime numbers.