boot sale vs sales event

boot sale and sales event both are nouns.

Word	Noun	Adjective	Verb	Adverb
boot sale	Yes	No	No	No
sales event	Yes	No	No	No

As nouns, sales event is a hypernym of boot sale; that is, sales event is a word with a broader meaning than boot sale:

boot sale: an outdoor sale at which people sell things from the trunk of their car
sales event: an occasion (usually brief) for buying at specially reduced prices

Other hypernyms of boot sale include cut-rate sale, sale.

boot sale (noun)	sales event (noun)
an outdoor sale at which people sell things from the trunk of their car	an occasion (usually brief) for buying at specially reduced prices