Practically speaking anything made from these grains including flour cake, cookies, pasta, breads, and items that have chametz as an ingredient, like malt are all chametz. Many perfumes and deodorants having a grain based alcohol may also be Chametz. Cat , dog and other pet foods may contain chametz.
In the Bible it says “and on the first day you should remove all se’or sourdough, which was used for a leavening, from your homes. Anyone who eats chametz (leaven) from the first day to the seventh day shall be cut off from Israel.”
Chametz is forbidden to be eaten from the 5th hour of the morning before Passover. The morning starts not from midnight but from daybreak. In the fifth hour benefit from the Chametz is forbidden, and before the 6th hour all chametz should be burned. Chametz is then completely forbidden till after Passover.