Final answer:
The toLowerCase() method returns a new String with all uppercase characters from the original string converted to lowercase. It does not return a byte, boolean, or int.
Step-by-step explanation:
The toLowerCase() method in programming languages such as Java and JavaScript returns a String that is a copy of the original string, with all uppercase characters converted to lowercase. The method does not modify the original string but instead returns a new string with the case conversion applied. For example, if you have a string 'Hello World' and you apply toLowerCase() to it, you would get 'hello world' as the result.