can someone please tell the use of double single inverted commas

Double inverted commas are used to while quoting exact words of a person or from a text.

For example:

He said,"I am going to the market."

The names of short stories, essays, journals, magazines are generally put in single inverted commas while writing them in a text.

For example

He purchased the novel 'Pride and Prejudice' from the book fair.