The option ‘-w’ means “Don’t print ‘\input fwebmac.sty’ as the first line of the .tex output file.” The option ‘-wfname’ means “Print ‘\input fname’ as the first line.” For example, when working with REVTeX (see REVTeX), one needs to say ‘-wrwebmac.sty’.
This option can be used for special effects when one is trying to obtain behavior different from that defined by FWEB’s macro package fwebmac.sty (see fwebmac.sty). However, try to not do that. Please submit requests for such behavior modifications to the developer; see Support.