Listing examples with や

Like と, や joins nouns, but や presents them as examples from a larger set. 本ほん や ペン means “books, pens, and other things” or “things such as books and pens.”

English can make this clear with “such as” or “among other things.” Japanese expresses it through や between the nouns, so you do not always need to spell out “and other things” in a natural English translation.

Choose や when you intend to give examples. 犬いぬ や 猫ねこ が 好すき です says you like animals such as dogs and cats. と is also grammatical, but presents dogs and cats as the particular set you are naming.