We can report people's words by using direct speech or indirect speech.
Direct Speech: Exact words of the speaker. We use quotation marks (' ').
Reported (Indirect Speech): Exact meaning of what someone said but not the exact words. We do not use quotation marks.
While reporting someone's sentences we start the sentences generally with some verbs like "say, tell".
eg: Tom said that it was nice to be at home.
SAY - TELL
Say is used with or without personal object.
Eg: He said (that) he was Ted.
He said to me (that) he was Ted.
Tell is always used with a personal object.
Eg: He told me (that) he was Ted.
We report someone's sentences after some time. Because of this, in reported speech we change personal pronouns, possessive adjectives/pronouns, verb tense, and time expressions according to the meaning of the sentence.
Eg: Sam said "I am flying to Italy with my family tomorrow."
Sam said that he was flying to Italy with his family the following day.
When the reported sentence start with past tense verb like "said, told" etc., the verb tenses change as follows:
Time expressions change like this:
(From Grammar Worm)