p10 to p8 in simple DES

I am new to cryptography.

During my learning I am facing prob in s-des. I am confuse from how P10 to P8 come, and confuse in the process of this algo. can anyone have any good article to solve it easily.

I am reading following example but getting confuse..


## Example ##

        P10 = { 3, 5, 2, 7, 4, 10, 1, 9, 8, 6}

        P8 = { 6, 3, 7, 4, 8, 5, 10, 9}

        K =     10100 00010

        P10     10000 01100

        LS-1    00001 11000  ->  P8  ->  K1 = 1010 0100

        LS-2    00100 00011  ->  P8  ->  K2 = 0100 0011