This was introduced in ES2015 to handle Unicode characters that cannot be represented by a single 16-bit Unicode unit, but need 2 instead.
Using charCodeAt() you need to retrieve the first, and the second, and combine them. Using codePointAt() you get the whole character in one call.
For example, this chinese character "𠮷" is composed by 2 UTF-16 (Unicode) parts:
"𠮷".charCodeAt(0).toString(16) //d842
"𠮷".charCodeAt(1).toString(16) //dfb7
If you create a new character by combining those unicode characters:
"\ud842\udfb7" //"𠮷"
You can get the same result usign codePointAt():
"𠮷".codePointAt(0) //20bb7
If you create a new character by combining those unicode characters:
"\u{20bb7}" //"𠮷"
More on Unicode and working with it in Unicode and UTF-8.