what are the content word?

Content words are the ones that refer to things, people and animals (= nouns); qualities, such as “big”, “intelligent”, “good”, etc. (= adjectives); actions, such as “to do”, “went”, “stayed”, etc. (= verbs); the way anything is done, such as “in a hurry”, “well”, etc. (= adverbs).

Function words, on the other hand, have little meaning on their own, such as “of”, “in”, “on” (= prepositions); “and”, “but” (= conjunctions); the, a, an (= articles).