Everyday 和 Every day 有什麼分別?

I go to school everyday. (wrong sentence)

"everyday" is an adjective. (每天的, 平日的)
e.g. Accidents are everyday occurrences. 事故天天發生。
She wears everyday clothes to work. 她著便裝上班。

I go to school every day. (correct)
"every day" is an abverbial phrase. (每天)