Saying exactly what someone has said is called direct speech (sometimes called quoted speech). Here what a person says appears within quotation marks. Indirect speech (sometimes called reported speech), doesn't use quotation marks to enclose what the person said and it doesn't have to be word for word. When reporting speech the tense usually changes. This is because when we use reported speech, we are usually talking about a time in the past (because obviously the person who spoke originally spoke in the past). The verbs therefore usually have to be in the past too. In this video Mrs. Santha A. Kumar explains this tense change in direct and indirect speech with relevant examples.
