Java is a software from Oracle, you can read its policy on the website: https://www.oracle.com/legal/privacy/privacy-policy.html
Java 2 Runtime Environment (J2RE) contains all you need to execute JAVA applications.
The Java(TM) SE Runtime Environment includes the JAVA Virtual Machine, runtime libraries and the necessary applications to launch programs written in JAVA language.
This pack is thought for users, not for developers, if you want to compile applications, you can download Java 2SDK Standard Edition.
Java Runtime Environment (JRE) stands for Java Runtime Environment, and is used to run Java platform applications. It is composed of libraries (APIs) and the Java Virtual Machine (JVM). It contains the necessary tools to run applications developed with Java technology and language on your computer.
Currently, many websites, online games, programs, chat programs, and 3D image viewers, among others, use Java technology, which makes it essential to install this program on your computer.
The Java Runtime Environment (JRE) is not a development environment, the tools for this function are not contained here. For this you must have the Java SE Development Kit (JDK) installed on your computer.
But… what is this “Java” and why is it so necessary?
The Java programming language is object-oriented and was developed in the 1990s by a team of programmers led by James Gosling, from the company Sun Microsystems. Unlike conventional languages, which are compiled to native code, the Java language is compiled to a “bytecode” that is executed by a virtual machine. The Java programming language is the conventional Java Platform, but not its only one.
The Java Virtual Machine (JVM) is a program that loads and runs Java applications, converting the “bytecodes” into executable code. The JVM is responsible for managing the applications as they run.
Programs written in the Java language can run on any hardware and software platform that has a version of the JVM, making these applications independent of the operating system platform on which they are operating.
Since the language’s release in May 1995, the Java platform has been the most rapidly adopted platform in the history of computing. In 2003 it had already reached the milestone of 4 million developers worldwide.
Today Java is a reference in the software development market and became popular for its use on the internet, having its execution environment present in web browsers, mainframes, operating systems, cell phones, palmtops and smart cards, among others.