Zilch is zero or nearly zero. This is a slangy term for nothing at all.
If you have nothing in your bank account, you have zilch. If you no money in your pockets, you have zilch. People usually use this word when they're being humorous or informal. A CEO would be unlikely to say zilch when speaking to shareholders. A friend who beats another friend 3-0 in air hockey is likely to say "I win, three to zilch!" Zilch can also be called aught, a goose egg, nada, naught, nil, nix, null, zip, or zippo.