what should i study to learn everything about cashu, ecash, bitchat, and hash rate ?

nostr:npub1sg6plzptd64u62a878hep2kev88swjh3tw00gjsfl8f237lmu63q0uf63m

nostr:npub12rv5lskctqxxs2c8rf2zlzc7xx3qpvzs3w4etgemauy9thegr43sf485vg

nostr:npub1s05p3ha7en49dv8429tkk07nnfa9pcwczkf5x5qrdraqshxdje9sq6eyhe

nostr:npub1qny3tkh0acurzla8x3zy4nhrjz5zd8l9sy9jys09umwng00manysew95gx

help!