Bash scripts start with the following line

    # Rest of script below

In `bash` the `#` character is the start of a comment, but `#!/bin/bash` is definitely not a comment, therefore [it isn't bash but the kernel][1] that interprets that statement.

So what exactly is that first line? Is it a specific language, or a special one-off case in the Linux kernel? Are there other commands or statements in this "language" that can be used when scripting?