Verb is a word which describes action. It shows what people or things are doing.
Here are some common verbs which are used normally.
Drink, Speak, Eat, write, jump, sing, look, walk, learn, swim etc are commonly used verbs.
The tense of a verb indicates time. The use of singular and plural forms indicates the quantity of things acting in a sentence.
Have a look at the following sentence.
I am playing cricket.
Here play is the verb and shows what action the subject is doing.
The form of verb must agree the subject. If the subject and verb agrees than only the sentence is grammatically correct.
Click on below link to see the rules of subject and verb agreement.