foreplay vs sexual activity

foreplay and sexual activity both are nouns.

Word	Noun	Adjective	Verb	Adverb
foreplay	Yes	No	No	No
sexual activity	Yes	No	No	No

As nouns, sexual activity is a hypernym of foreplay; that is, sexual activity is a word with a broader meaning than foreplay:

Other hypernyms of foreplay include sex, sex activity, sexual practice.

foreplay (noun)	sexual activity (noun)
mutual sexual fondling prior to sexual intercourse	activities associated with sexual intercourse