A compound subject is two or more subjects for a single verb. When the subjects are connected by and, the verb is usually plural.
Spaghetti and meatballs is my favorite dinner. A compound subject preceded by each or every takes a singular verb.
Every new book and journal is catalogued before it is shelved.
When compound subjects are joined by or or nor, the verb agrees with the nearest subject word.
Neither moon nor stars were visible. (The plural noun, stars, takes a plural verb, were.)