If you ever been to court or if you have ever watched a television show specifically Judge Judy you often hear the judge say you can’t tell me what someone said that is unless they are present to testify otherwise it is hearsay.
The reason why judge’s say “don’t tell me what someone said, that’s hearsay” because it may not be accurate or the truth as he/she is not sworn under oath or affirmed under penalty of perjury that they will to tell the whole truth and nothing but the truth.
Here’s an example if you have even played the game “Telephone”. Telephone is you write something down on a piece of paper let’s assume that you write “I like to eat cheese pizza” just for the record, you then whisper that to the person on your left for example, they then do this again until it reaches the last person who should be sitting next to you. The last person in which they should get up and say what they were told hopefully it is “I like to eat cheese pizza”, if it is anything else that means somebody didn’t hear something correctly or the added something that they shouldn’t have.