When you download software online, what are you downloading exactly?
Are you downloading pre-compiled source code?
Are you downloading post-compiled machine code?
It varies. I use Linux, so I do the former (if you meant pre-compilation source code) a lot more than most people.
But it varies with languages too, to some extent. If you're running a "web app" inside a browser, chances are it's using JavaScript source code that's interpreted by the browser. Some interpreted languages have "compilers" that actually bundle a binary of the interpreter with the source code. Others, like Java and MS .NET apps, compile to a machine code, but for a "virtual machine". A separate binary runs the virtual machine with the app. Though in the .NET case there's usually just enough true machine code to start up the virtual machine which is in a DLL.
In most cases, when you download a binary, it is pre-compiled, post-compilation machine code - for your real machine or the Java or .NET virtual machine. And in most cases when you install software it's pre-compiled, post-compilation machine code - for your real machine or the Java or .NET virtual machine.