We use quotation marks to show that a phrase was spoken by someone. We can only use quotation marks for direct speech; we write exactly what someone said.
If you are explaining what someone said without writing the exact words, it is called reported speech, and it doesn't need quotation marks.
You need to put a quotation mark at the beginning and end of the spoken information. Other punctuations marks (such as full stops and commas) go inside the quotation marks.
A witness sitting in a nearby cafe said, "I heard a loud bang and then there was smoke everywhere." Other people also told us they saw smoke and flames coming from the building.
The quotation marks show us the the witness's exact words were "I heard a loud bang and then there was smoke everywhere". The rest of the information is the writer's interpretation.
We also use quotation marks to write a conversation between people.
"Are you enjoying the holiday?" asked Kate.
"Yes," replied Sam, "I'm having a great time."
Remember, only the words that someone actually says go in the quotation marks.