Doubts about netfilter + nftables and module

[Elias Valea Peri <eliasvp@gmail.com>]

Hi to all, we’re migrating our systems from netfilter + iptables to
netfilter + nftables.
We’re looking for information about which modules we want/need to load
for our needs and extensions we want to use.
Looking for documentation about, we aren't capable to find a
description of what does each module. For some modules, we see easily,
just by its filename, what does but for others it isn't easy.
We've downloaded our kernel sources, look for doc at netfilter.org,
www.kernel.org/doc, etc... without success.
Does anybody knows where we can find for each nf_*.ko, nfnetlink_*.ko,
nft_*.ko ... file the functionality/extension that implements each one
????

Thanks a lot for your help

Elias