Update README.md with image descriptions

README.md

@@ -46,12 +46,49 @@ AWS security directly.
 
 ## Why does security scanner show that a docker image has a CVE?
 
-If a security scanner reports that an amazoncorretto image includes a CVE, the first recommended action is to pull an updated version of this image.
+If a security scanner reports that an amazoncorretto image includes a CVE, the first recommended action is to pull an updated version of this image with `docker pull amazoncorretto:<tag>`.
 
 If no updated image is available, run the appropriate command to update packages for the platform, ie. run "apk -U upgrade" for Alpine or "yum update -y --security" for AmazonLinux in your Dockerfiles or systems to resolve the issue immediately.
 
 If no updated package is available, please treat this as a potential security issue and follow [these instructions](https://aws.amazon.com/security/vulnerability-reporting/) or email AWS security directly at [[email protected]](mailto:[email protected]).
 
-It is the responsibility of the base docker image supplier to provide timely security updates to images and packages. The amazoncorretto images are automatically rebuilt when a new base image is made available, but we do not make changes to our Dockerfiles to pull in one-off package updates.  If a new base image has not yet been made generally available by a base docker image maintainer, please contact that maintainer to request that the issue be addressed.
+It is the responsibility of the base docker image supplier to provide timely security updates to images and packages. The amazoncorretto images are automatically rebuilt when a new base image is made available, but we do not make changes to our Dockerfiles to pull in one-off package updates. If a new base image has not yet been made generally available by a base docker image maintainer, please contact that maintainer to request that the issue be addressed.
 
 Note that there are multiple reasons why a CVE may appear to be present in a docker image, as explained in the [docker library FAQs](https://github.com/docker-library/faq/tree/73f10b0daf2fb8e7b38efaccc0e90b3510919d51#why-does-my-security-scanner-show-that-an-image-has-cves).
+
+Security scanners may use heuristics or version checks of packages compared to a security advisory to determine if an image is potentially vulnerable. The generic Linux Corretto RPMs use a slightly different version than packages built specifically for Amazon Linux, images are available for both package types. When an Amazon Linux Security Advisory (ALAS) bulliten is published it will include the Corretto package name and version that contains the fix and that version will not correctly match the generic Linux package. 
+
+## Types of images provided
+
+**amazoncorretto:<version>**
+The default image based on Amazon Linux 2, using the Corretto generic Linux RPM packages. The Corretto packages installed support a wide range of Linux versions, and not all GUI dependencies are installed. The Corretto generic linux packages use a slightly different version scheme than native packages, which may not match exact versions posted in ALAS bulletins. However, both generic linux and native Amazon Linux packages will contain the same code.
+
+**amazoncorretto:<version>-alpine**
+Based on [Alpine Linux](https://www.alpinelinux.org/) that uses [musl libc](https://musl.libc.org/), with a focus on smaller image sizes. Images are available for each supported Alpine version. When new versions of Alpine come out, a pre-built image is typically provided on the next Corretto security release after the base image is available.
+
+**amazoncorretto:<version>-al2-native**
+Based on Amazon Linux 2 using the Corretto RPMs specifically built for the platform using the platform’s toolchain. These will include all dependencies, and the version of the Corretto packages will match ALAS bulletins.
+
+**amazoncorretto:<version>-al2023**
+Based on Amazon Linux 2023 using the Corretto RPMs specifically built for the platform using the platform’s toolchain. These will include all dependencies and the version of the Corretto packages will match ALAS bulletins.
+
+**amazoncorretto:<version>-debian**
+The dockerfiles are provided as examples only. Corretto is supported on `apt`/`deb` based distributions, but does not provide pre-built images.
+
+### Image subtypes
+
+#### Corretto 8
+**jre** - Contains only the runtime components and not the compiler. Suitable for most services.
+
+**jdk** - Full development environment with compiler and tools.
+
+#### Corretto 11+
+**headless** - Contains runtime components without GUI libraries and dependencies. This will be the smallest image and is suitable for most services.
+
+**headful** - Runtime components with GUI libraries and dependencies.
+
+**jdk** - Full development environment with compiler and tools.
+
+### Version Tags
+
+Image tags contain either just the major version or a specific security update version. Corretto 8 version tags have a format of `8u<security_update_version>`, for example `8u402` . Corretto 11 and later use `<major_version>.0.<security_update_version>`, for example `11.0.22` . Images for a major version always point to the latest security update. Once a new security update version is released, the old tag no longer gets base image updates but remains available.