This is the 7819th most frequent Portuguese word.
queijo
Cheese.
In this sentence, 'queijo' is used as a noun to refer to the food item, 'cheese'.
Eu gosto de comer pão com queijo.
I like eating bread with cheese.
Here, 'queijo' again functions as a noun, indicating the subject about which the fact is stated.
Queijo é feito principalmente de leite.
Cheese is mainly made of milk.
In this sentence, 'queijo' remains a noun, describing the type of object associated with the adjective 'envelhecido' ('aged').