If you are not sure which Java package to install, the general recommendation is to install to the default OpenJDK (JDK 11) version. The JDK includes the JRE and development/debugging tools and libraries necessary to build Java applications.

The JRE consists of the Java virtual machine (JVM), classes, and binaries that allow you to run Java programs. The default Ubuntu 20.04 repositories include two OpenJDK packages, Java Runtime Environment (JRE) and Java Development Kit (JDK). Permits only non-commercial use of the software, such as personal use and development use. OpenJDK and Oracle Java are the two main implementations of Java, with almost no differences between them except that Oracle Java has a few additional commercial features. There are multiple different implementations of Java. You can find applications developed in Java on your laptop, phone, and game console.

Java runs on all major operating systems and devices. Java is one of the most popular programming languages used to build different kinds of applications and systems. How to Install Java on Ubuntu - ImagineLinux

Openjdk install