Quotation marks (' . . . '  "... ") can also be called 'inverted commas'.

1)    We can use quotation marks when we say what name something has.
. . . can be called 'inverted commas'. And quotation marks are often used when we mention titles.

• His next book was 'Heart of Darkness'.

2)    We can use quotation marks when we mention a word, or when we use it in an unusual way.

• The word 'disinterested' does not mean 'uninterested'.
  
• A textbook can be a 'wall' between a teacher and a class.

3)    We use quotation marks (single ' ... 'or double "... ") when we quote direct speech.

• 'Hello,' she said. OR "Hello," she said.