[noun] + もまた
もまた is a weightier "too", "likewise": X, just like the thing mentioned before, is also this way. It goes straight after a noun, in the slot where は, が or を would stand, and it is almost always written in kana; the kanji また又 is rare.
The particle it replaces disappears: ×彼はもまた, ×彼がもまた.
Both mean "too". Plain も is what you say; もまた adds weight and belongs to essays, speeches and fiction. In conversation もまた sounds stiff or dramatic.
Because it draws a parallel with something already said, もまた often sums up an idea in a short general statement, the way "too" does in "history, too, repeats itself".