Verbs are the most important part of a sentence and are used to express an action or state of being. There are different types of verbs:
Linking verbs: express states of being and are considered the equals sign in a sentence, i.e. the thunder is loud.
Auxiliary verbs: are small words that assist the main verb in expressing a meaning, asking a question or forming a particular tense. They consist of: to be; to do; and to have. i.e. she will answer the question, he has made an error.
Verbs can also change depending on whether it is in the first, second or third person, and singular or plural in number.
Verb tense also indicates the time of the action or state of being, it also indicates if it is completed or ongoing. There are six standard tenses:
Present simple Past simple Future simple
Present perfect Past perfect Future perfect
A good copyeditor/proofreader will ensure verb agreement and use of tenses are correct within your document.
Your local library will have lots of great grammar books you can borrow, many with exercises you can do to test and improve your knowledge of grammar.