What is Blockchains 12 word recovery passphrase process Hello thank you for looking.

I am trying to discover a simple way of creating blockchains 12 Word Recovery Passphrase, they have a so called help page on this subject which is of very little help and profoundly obscure, your help would be greatly appreciated.

Kind Regards

Richard Norman
You secret key is a set of 256 random ones and zeros (bits). This is very difficult to remember. So, we need to represent those ones and zeros differently. 


Create a checksum of the private key by taking the first (entropy-length/32) bits of its SHA256 hash.
Add the checksum to the end of the random sequence.
Divide the sequence into sections of 11 bits.
Map each 11-bit value to a word from the predefined dictionary of 2048 words.
The mnemonic code is the sequence of words.


Source: https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki