Oracle JDK (Java Development Kit) is a set of software tools and libraries that developers use to create Java applications. It includes the Java Runtime Environment (JRE), the Java Compiler (javac), and various development tools and utilities. Oracle JDK was historically one of the most widely used JDK distributions for Java development.  Oracle made changes to its licensing and distribution model for Oracle JDK.

Here are some key points regarding Oracle JDK:

1. Licensing Changes: Oracle introduced a new subscription-based licensing model for Oracle JDK starting with JDK 11. This means that Oracle JDK is no longer free for commercial use in production environments. Free public updates for Oracle JDK 8, the last free long-term support (LTS) release, 

2. Oracle JDK vs. OpenJDK: OpenJDK (Java Platform, Standard Edition Open Source Implementation) is an open-source project that provides the reference implementation of the Java platform. Oracle JDK is based on OpenJDK and includes some additional features and tools.

3. Alternatives to Oracle JDK:

   • OpenJDK: Many developers have transitioned to using OpenJDK, which is functionally equivalent to Oracle JDK. It is open source and free to use.
   • Oracle also offers Oracle JDK with commercial support, which organizations can subscribe to for long-term support and updates.

4. Java SE Development Kit Releases: Oracle JDK had releases for versions 8, 11, and later. Each release had its own set of features, enhancements, and support timeline.

5. Choosing a JDK: When choosing a JDK for your project, consider factors such as licensing requirements, long-term support, and compatibility with your application. OpenJDK has become a popular choice for many projects due to its open-source nature and compatibility with the Java platform.