rest area vs layby

rest area and layby both are nouns.

Word	Noun	Adjective	Verb	Adverb
rest area	Yes	No	No	No
layby	Yes	No	No	No

As nouns, rest area and layby are synonyms defined as:

rest area and layby: designated paved area beside a main road where cars can stop temporarily

Other synonyms of rest area include lay-by, pull-off, rest stop.

rest area (noun)	layby (noun)
designated paved area beside a main road where cars can stop temporarily	designated paved area beside a main road where cars can stop temporarily