Verbs are either active or passive in voice. In the active voice, the subject and verb relationship is straightforward: the subject is a do-er. In the passive voice, the subject of the sentence is not a do-er. It is shown with by + do-er or is not shown in the sentence.
Passive voice is used when the action is the focus, not the subject. It is not important (or not known) who does the action. 

• The window is broken. (It is not known who broke the window, or it is not important to know who broke the window.)
• The class has been canceled. (The focus is on the class being canceled. It is not important to know who canceled it.)

Reported Speech is used to tell or report what someone has said.

For example, look at this sentence: Jim said, "I love Eshika." If we ask someone else to tell us what Jim said, the person would say (or report) what the first person said like this.

He said he loved Eshika. 
Or Jim said he loved Eshika.

But notice how the verb tense changed. Love became loved. Here are some rules...

The present tense verb is change to the past tense in reported speech.

Sujana said, "I like pizza."

What did she say? 
She said (that*) she liked pizza.

The past tense is change to the past perfect in reported speech.

Joe said, "I went to New York City."

What did he say?
He said (that) he had gone to New York City.

The present continuous is changed to the past continuous.

Michael said, "I am taking an English class."

What did he say?
He said (that) he was taking an English class.

The present perfect verb is change to the past perfect tense in reported speech.

Michelle said, " I have been to California."

What did she say?
She said (that*) she had been to California.

The past perfect tense doesn't change.

John said, " I had talked to my neighbor."

What did he say?
John said (that) he had talked to his neighbor.

The future tense verb is change to the conditional in reported speech.

Sujana said, "I will buy a new house."

What did she say?
She said (that) she would buy a new house.

*You can use the word that in reported speech if you want. It doesn't matter if you do or not.

Passive voice should be avoided when you want more clarity in writing. However, in some cases, you need to use passive voice to stress the action, not the actor. Also, passive voice can be considered more polite, as it sounds less aggressive or dramatic. 

• That building was built in 1990.
• The car was invented about a hundred years ago.
• I was told that Mary moved to a different country.
• Your business is appreciated.
• She was elected to city council.
• It was rumored that the company would lay off a few people soon.
• It is recommended that the billing process be shortened.