A huge amount of software exists in the world, controlling the systems that enrich our lives. Some code is really obvious, such as operating systems like Windows, web sites, and video games. Some is not so obvious, for example the embedded code that controls our microwave, our thermostat, or our car engine.
What are we doing when we write code?
Note on Compilers: Some languages also need a compiler to run: an application that turns code into a package that can then be run to create an output. Flash is an example of a compiled language — you create some Flash source code, then compile it into a Flash Movie. A web browser with the Flash Player plugin installed can then display this Flash movie, which is its own standalone little block; the source code is no longer readable.
Interpreted languages are often easier to learn than compiled languages, because with interpreted languages you can just open up the source code and see how it works. You can’t do that with compiled languages because the language is converted into a non-human readable form when compiled.