where can I find the file name specification that tells me what each field is and what they mean?

If by "file name specification that tells me what each field is and what they mean" you mean "the name of the file that documents all of the named packet fields", then there's no file that's shipped with Wireshark, but there is a reference for all the named fields. (That page should call them "named fields", not "display filters", because they're useful for more than just display filtering.)

The description of the field is taken from the Wireshark code; it is not necessarily a detailed description of the field. For a detailed description of a field for a particular protocol, you'll probably need to read some form of specification for the protocol or tutorial for the protocol; we do not have a list of those.