Compiling is the process of transforming a computer program written in a given language into a set of instructions in another format or language. A compiler is a computer program to execute that task.
Typically, a compiler transforms code written in a higher-level language such as C++ or Rust or Java into executable (runnable) code — so-called binary code or machine code. WebAssembly, for example, is a form of executable binary code that can be compiled from code written in C++, Rust, C#, Go, Swift, and several other languages and that can then be run on any web page, in any browser.
Most compilers perform either ahead-of-time (AOT) compilation or just-in-time (JIT) compilation.
gcc compiler is one well-known example of an AOT compiler. AOT compilers are typically invoked from the command line in a shell environment (from within a terminal or console) or within an IDE.