Agreement between a verb and its subject for number and person.
English requires that verbs agree with their subjects in number and person. In simple cases, the English agreement system is extremely sparse, as the only form that requires a special agreement marker is the third-person singular
The verb to be is the only exception to this rule, as it also carries a special form for the first-person singular:
Questions with this tag generally deal with more complex issues such as verb agreement with multiple subjects, or when the subject noun phrase has both a singular part and a plural part.