I understand differences btw Oracle Jdk, OpenJdk, AWS Corretto.
I know AWS team maintains Corretto, gives long term support for free but OpenJDK also has LTS support (8, 11, 17, ..) so other than Amazon adding fixes faster, I see no other benefit in Corretto.
If both OpenJdk and Corretto provide LTS, what is the point of using Corretto?
UPDATE
https://github.com/corretto gave me answers regarding the versioning confusion I had.
but OpenJDK also has LTS support (8, 11, 17, ..)
Be careful with your use of names here.
OpenJDK is the name of an open-source project. That project implements the Java specifications published by Oracle. The OpenJDK project is owned by Oracle Corp but enjoys the contributions of code and labor by IBM, Apple, and other companies and individuals.
The OpenJDK project provides only source code. For executable builds of that software, and installers for that software, you must look elsewhere. Several vendors offer binaries and installers.
The confusion comes from the fact that Oracle Corp legally allows vendors to use the word “OpenJDK” in the name of their JDK products. This naming represents the fact that their product is based largely (if not entirely) on the OpenJDK source code.
what is the point of using Corretto
You have a choice of obtaining a JDK (implementation of the Java specs) from several vendors. You may have various reasons motivating your choice. One reason might be the possibility of purchasing a support plan. Another reason might be needing an implementation for a particular less-common platform. Another reason might be convenience, or familiarity with the vendor.
Some folks choose AWS Corretto because they intend to deploy on AWS cloud. Amazon promises to keep Corretto as close as is practicable to the same as what executes on the AWS cloud.
Why is Corretto so behind given that OpenJDK LTS is 17 and Correto is based on OpenJdk 11?
As explained well in the Answer by dave_thompson_085, your understanding of those versions is incorrect.
Amazon maintains releases of Corretto for all three long-term support (LTS) versions of Java: 8, 11, and 17. Amazon also has a release for the current version of Java, 19.
The version number of each Corretto release corresponds with the version of Java specs being implemented, as noted on their GitHub site.