JDK 1.8, also known as Java 8, was a significant release of the Java platform by Oracle. It introduced several important features and enhancements to the Java programming language. Here are some key features and changes introduced in Java 8:

1. Lambda Expressions: Java 8 introduced lambda expressions, which allow you to write concise and expressive code for defining inline functions or anonymous functions. Lambda expressions are especially useful when working with functional interfaces.

2. Streams: The Stream API was introduced, providing a powerful way to work with sequences of data in a functional style. Streams allow you to perform operations like filtering, mapping, reducing, and collecting data from collections or other sources.

3. Functional Interfaces: Java 8 introduced functional interfaces, which are interfaces with a single abstract method. Functional interfaces are a key concept in lambda expressions and provide the foundation for functional programming in Java.

4. Default Methods: Default methods allow interfaces to have method implementations. This feature was introduced to maintain backward compatibility when adding new methods to existing interfaces.

5. Method References: Java 8 introduced method references, which provide a shorthand notation to refer to methods or constructors using the :: operator. Method references are closely related to lambda expressions.

6. New Date and Time API: Java 8 introduced the java.time package, which provides a modern date and time API that addresses the limitations and complexities of the previous java.util.Date and java.util.Calendar classes.

7. Optional: The java.util.Optional class was introduced to represent an optional value that may or may not be present. It helps avoid null references and NullPointerExceptions.

8. Nashorn JavaScript Engine: Java 8 included the Nashorn JavaScript engine, which allowed you to execute JavaScript code from within Java applications. It provided improved performance compared to the older Rhino engine.

9. New APIs and Libraries: Java 8 introduced various new APIs and libraries, including the CompletableFuture class for asynchronous programming, the Collectors class for working with streams, and more.