What is the purpose of Escape Sequence \' in java?

if I print ' (single quote) in the System.out.println() I can get exact output.

Like :

System.out.println("test'test");
output:  test'test

What is the purpose of using \' escape sequence in java?

This also gives me the same output.

 System.out.println("test\'test");
 output:  test'test

pls explain what is the main purpose of \' escape sequence in java