What is Carrier Grade Nat (in human readable language!)?

I googled Carrier Grade NAT (CGN) and read some articles on Wikipedia and other websites, but I did not understand its difference with traditional CPE-NAT.

Are CGN and CPE-NAT two totally different tools or CGN has some features (such as XLAT464, Dual-Stack Lite, and Port Control Protocol) more than CPE-NAT?

Carrier-Grade NAT just means the ISP is doing NAT and the customers don't get public IPv4 addresses. Exactly why a given ISP is doing this or what features their NAT has can vary.

The IETF (the Internet standards body) has a "Best Current Practices" document, BCP 127, RFC 6888 giving requirements for a well-implemented CGN. However, as with anything, not everyone follows the best current practices.