Reported speech is used to report statements, questions or commands. It allows you to express the meaning of what somebody  has said without using the speaker's exact words:

Sandy is talking to her hairdresser:  Oh, James is so romantic! He came into my office  with a bouquet of roses and asked me to marry him.

Will you  marry me?

  When you use indirect speech to report someone's words, some changes in tenses, pronouns, adverbs, etc. are often necessary.