Literally, it’s a page break (“form feed”) character. The compiler treats it as ordinary whitespace. But it’s very useful for printing source code – it starts a new page (for example, use ^L between functions to force each call to get its own page).
In Vim/vi based editors, you can insert such a character within edit mode by typing Ctrl + V followed by Ctrl + L. It will look like ^L in the editor, but it’s actually just one character (ASCII value: 12 or 0x0C).
In other words, ^L does this:
