cut --help and man cut can teach you more than anyone here.

But: “|” takes the output of the former command, and uses it as input for the latter. So it’s like copying the output of “echo […]”, executing “cut -d ‘/’ -f 6”, and pasting it into that. Then copy the output of “cut”, execute “base64 -d” and paste it there. Except the pipe (“|”) automates that on one line.

And yes, cut takes a string (so a list of characters, for example the url), split’s it at what -d specifies (eg. cut -d ‘/’ splits at “/”), so it now internally has a list of strings, “https:”, “”, “link.sfchronicle.com”, “external”, 41488169.38548", “aHR0cHM6Ly93d3cuaG90ZG9nYmlsbHMuY29tL2hhbWJ1cmdlci1tb2xkcy9idXJnZXItZG9nLW1vbGQ_c2lkPTY4MTNkMTljYzM0ZWJjZTE4NDA1ZGVjYSZzcz1QJnN0X3JpZD1udWxsJnV0bV9zb3VyY2U9bmV3c2xldHRlciZ1dG1fbWVkaXVtPWVtYWlsJnV0bV90ZXJtPWJyaWVmaW5nJnV0bV9jYW1wYWlnbj1zZmNfYml0ZWN1cmlvdXM” and “6813d19cc34ebce18405decaB7ef84e41”, and from that list outputs whatever is specified by -f (so eg. -f 6 means the 6th of those strings. And -f 2-3 means the 2nd to 3rd string. And -5 means everything up to and including the fifth, and 3- means everything after and including the third).

But all of that is explained better in the manpage (man cut). And the best way to learn is to just fuck around. So echo “t es t str i n g, 1” | cut … and try various arguments.