A runtime environment is code that provides the necessary resources and services for executing and running applications in a certain programming language.
The runtime typically provides a layer of abstraction between the code and the underlying hardware and operating system. It manages memory, handles exceptions, and provides other services that the code needs to run correctly. The runtime may also include a just-in-time (JIT) compiler or interpreter that translates the code into machine code, which the computer can understand and execute.
The runtime is specific to the programming language and can vary between different implementations of the language. For example, the runtime for Java is the Java Virtual Machine (JVM), which is responsible for executing the compiled Java bytecode. Similarly, the .NET runtime (CLR) is responsible for executing code written in languages such as C# and Visual Basic .NET.