This is the 2905th most frequent Japanese word.
もり
"もり" (mori) means "forest" in English.
In this sentence, '森' refers to a forest, illustrating its use as a noun to describe a natural area densely populated with trees.
森の中には多くの生き物が住んでいます。
Many creatures live in the forest.
Here 'もりもり' is an adverb, indicating vigorous or energetic action, modifying the verb '食べる' (to eat).
もりもり食べることで元気が出ますよ。
Eating heartily gives you energy.
'盛り' in '盛り付ける' (to plate) functions as a noun derived from the verb '盛る', meaning to heap or pile, often used in culinary contexts.