The verb in a sentence matches the subject in terms of number (Singular verb or plural verb). 

Simply singular subjects require singular verbs. Plural subjects require plural verbs.

It may be confusing to decide if the subject is singular or plural when using compound subjects (two or more subjects), collective nouns as subject (team, army etc), or subjects like "everyone", "some one" etc. 

 Here are 30 simplified rules for subject-verb agreement to avoid confusion and grammar errors.