Hi everyone I have recently gotten into trying to understand the math behind Bitcoin and cryptography.
Right now I am concentrating on the SHA-256 process mostly using http://www.righto.com/2014/09/mining-bitcoin-with-pencil-and-paper.html & https://en.wikipedia.org/wiki/SHA-2#Pseudocode & https://csrc.nist.gov/csrc/media/publications/fips/180/4/final/documents/fips180-4-draft-aug2014.pdf as a starting point

I have trouble understanding the following:
Where does the Wt value comes from, how to calculate it and how it relates to the previous block. I cannot understand the origin of this value at all.


Thank you

Edit:

Basically I am trying to understand this:

W_t =

M_t ⁽ⁱ⁾ for ≤ t ≤ 15

ROTL¹ (W_t−3 ⊕W_t−8 ⊕W_t−14 ⊕W_t−16 ) for 16 ≤ t ≤ 79