When you own stock, there is an actual certificate to indicate that you own a piece of that company. In a closely held corporation, you may actually receive the certificate to hold in your hand. If you own a corporation and want to issue stock, you can hand out actual certificates to the recipients. (Incidentally, the same thing happens if you buy stock from a publicly traded company through a broker. The broker probably deals in large volumes of that company every day, so they hold on to the certificates. Ask your broker if you can see your certificates.)
LLCs need certificates too--membership certificates. They are similar to stock certificates.
Our kit and seal comes with personalized stock certificates and a seal embosser and is available when you form a new company or a la carte. If you just want the certificates, you can order them separately. Our price is $1 each with a minimum order of 20. Be sure to mention whether you want certificates for a corporation or LLC.