A runtime environment is a collection of software tools and services that allow programs to execute on a computer. It provides the necessary resources, such as memory and processing power, and manages the execution of code. This environment ensures that the program runs smoothly by handling tasks like memory allocation and input/output operations. Different programming languages have their own specific runtime environments. For example, the Java Virtual Machine (JVM) is a runtime environment for Java applications, enabling them to run on any device that has the JVM installed. Similarly, Node.js serves as a runtime environment for executing JavaScript code outside of a web browser.