what is the purpose of the split on a string code example

Example 1: split string

const str = 'The quick brown fox jumps over the lazy dog.';

const words = str.split(' ');
console.log(words[3]);
// expected output: "fox"

const chars = str.split('');
console.log(chars[8]);
// expected output: "k"

const strCopy = str.split();
console.log(strCopy);
// expected output: Array ["The quick brown fox jumps over the lazy dog."]

Example 2: split on . in java

String textfile = "ReadMe.txt";
String filename = textfile.split("\\.")[0];
String extension = textfile.split("\\.")[1];

Example 3: split on . in java

String textfile = "ReadMe.txt";
String filename = textfile.split(".")[0];
String extension = textfile.split(".")[1];