Text : Forward Chain : Filters packets destined for networks protected by the firewall. Meaning : Filters packets that are determined beforehand for networks (it not "the networks") protected by the firewall. I think it is the private networks. Packets that come from the outside world into the private network. A firewall is normally a firewall for outside world and not for the private network. Table comes first and then comes Chain. Table here means a set of data arranged in rows and columns. Filter chains means to restrain using a series of related or connected facts,events etc.
P.S I do not guarantee about the correctness of the above statements.