preschool vs playschool

preschool and playschool both are nouns.

Word	Noun	Adjective	Verb	Adverb
preschool	Yes	No	No	No
playschool	Yes	No	No	No

As nouns, playschool is a hyponym of preschool; that is, playschool is a word with a more specific, narrower meaning than preschool:

preschool: an educational institution for children too young for elementary school
playschool: a small informal nursery group meeting for half-day sessions

Other hyponyms of preschool include kindergarten, nursery school, play group.

preschool (noun)	playschool (noun)
an educational institution for children too young for elementary school	a small informal nursery group meeting for half-day sessions