What is run time environment?

Distinguish this from Development Environments and Build Environments.

You will tend to find a hierarchy here.

Run time environment - Everything you need to execute a program, but no tools to change it.

Build environment- Given some code written by someone, everything you need to compile it or otherwise prepare an executable that you put into a Run time environment. Build environments are pretty useless unless you can see tests what you have built, so they often include Run too. In Build you can't actually modify the code.

Development environment - Everything you need to write code, build it and test it. Code Editors and other such tools. Typically also includes Build and Run.

Yes, including all the settings (like environment variables), common libraries(!), directory structure, network neighbors e.t.c

The runtime environment can also be a virtual machine, such as the JRE (Java Runtime Environment) or CLR (Common Language Runtime) for .NET framework.

What is the target of your program? Does the program run on top of the JRE, CLR? Or are you compiling into a binary file that is run by your operating system?

The main question is what is that target of your program. How will your program be executed?

As soon as a software program is executed, it is in a run-time state. In this state, the program can send instructions to the computer's processor and access the computer's memory (RAM) and other system resources. RTE allows the program to be run in an environment where the programmer can track the instructions being processed by the program and debug any errors that may arise. While developers use RTE software to build programs, RTE programs are available to everyday computer users as well,e.g software such as Adobe Flash Player

Source

To add to the other answers given, I would say that Runtime environment is an environment, which supports the execution of a program/process. A program, for being able to execute, requires runtime environment. Runtime environment provides following services to the program/process :-

• Resident Memory
• Resources such as File, Sockets, etc.
• Environment variables
• Proper initialization
• Proper disposal.

In short, Runtime environment is for the program, what physical environment is to us. Program/process can't sustain without runtime environment.