Understanding what is being run through Sha256
When that "hex" check box is ticked, it tells the website to interpret the hex string that you entered as representing hexadecimal bytes, i.e. binary data. Normally when you just hash that hex string, it is interpreted as a string, i.e. a sequence of characters. But you really want to hash the binary data that that string represents, and that is what that hex checkbox lets you do.