(cont.) The code pointer point to "word routines". These
routines expect to be called with IY pointing to the PF. They
themselves are expected to end by jumping to the address at
(IP). They will usually do so with "jp next".

That's for "regular" words (words that are part of the dict
chain). There are also "special words", for example NUMBER,
LIT, FBR, that have a slightly different structure. They're
also a pointer to an executable, but as for the other fields,
the only one they have is the "flags" field.