What is chametz and why should we sell it?

Any flour of the five species of grain, which is mixed with water and allowed to ferment before being baked, comes under the definition of chametz according to the Torah. The five species of grain are wheat, spelt, oats, barley, and rye.

Chametz may not be consumed on Passover, either by eating it, or dissolving it in water and drinking it, and no benefit may be derived from it. It must be either burned or destroyed of in some manner.

Even a minute particle of chametz is forbidden on Passover. Even if the amount of chametz in a mixture is only 1/1000th of the total, the entire mixture is forbidden as chametz!
 

 
A person who owns a large quantity of chametz which he is reluctant to dispose of, because doing so may cause him considerable financial loss, may sell his chametz to a non Jew.

After writing a bill of sale, one may leave the chametz in his home without transgressing the prohibitions of not seeing or having chametz, since the chametz no longer belongs to him.

However, it must be set aside in a special place which is rented to the non Jew who has purchased it, so that the chametz becomes the property of the non Jew until after Passover.

The place where this sold chametz is stored should be inaccessible, so that neither he nor the members of his family take anything from there through force of habit. The bill of sale for the chametz states that he is selling his chametz to the non Jew for a specific price. The non Jewish purchaser then gives him a down payment either money or something with intrinsic value, to acquire ownership of the chametz.

A stipulation is added to the bill of sale, stating that if the purchaser does not pay the balance due by the end of Passover, the chametz will revert to the original owner at that time that is, at the end of Passover. The non Jew's failure to pay will not be seen as having retroactively invalidated the sale. 
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Delegation of Power to Sell Chometz

I the undersigned, fully empower and permit Rabbi Shimon Heidingsfeld to act in my place and stead, and on my behalf to sell all chametz possessed by me, knowingly or unknowingly as defined by the Torah and Rabbinic Law (e.g. chametz, possible chametz, and all kind of chametz mixtures).

Also chametz that tends to harden and adhere to inside surfaces of pans, pots, or cooking utensils, the utensils themselves, as well as pet food that contain chametz and mixtures thereof.

Rabbi Shimon Heidingsfeld is also empowered to lease all places wherein the chametz owned by me may be found, particularly at the address/es listed below, and elsewhere.

Rabbi Shimon Heidingsfeld has full right to appoint any agent or substitute in his stead and said substitute shall have full right to sell and lease as provided herein.

Rabbi Shimon Heidingsfeld also has the full power and right to act as he deems fit and proper in accordance with all the details of the Bill of Sale used in the transaction to sell all my chametz, chametz mixtures, etc., as provided herein. This power is in conformity with all Torah, Rabbinic and Civil laws.