We can use reported speech when we want to express someone what other people said. In this part we change the tense, the pronoun and we can use verbs as say, tell or ask.

Direct speech: It is the literal words that someone said, there isn't change in the tense and the easy way to identify direct speech is due to the quotation marks.

For example: The teacher said, "I finished my explanation" 

Reported speech: There are changes in the tense (as the image shows) in the pronouns and those sentences aren't the exact words

For example: The teacher told us he had finished his explanation.

For reporting yes or not questions for example with auxiliaries as Do or  verb to be,  we can use "if"or "whether". However, if they are "WH questions" we don't use if or whether, we use the same "WH questions" (what, where, why etc.) on the other hand, we use asked instead of said or told.

For example: Maria asked, "where can I find a bank?

Maria asked me where she could find a bank. 

As the tense changes, the adverbs of time change as well, for that reason we cannot use the same adverb, this changes  for anothe as the chart is shown.