Kitniyot in Hebrew is “legumes.” However, during Passover, it refers to the following grains: Wheat, Spelt, Barley, Oats and Rye. Today in Orthodox Judaism, it also includes other grains and legumes. These include Rice, Peas, Corn, Lentils and Beans. During Passover, all of these items are considered forbidden for Ashkenazi Jews around the world.
I won’t get into all of the historical details and minchagim (customs), but one of the main thoughts as to why these items are forbidden is that in ancient days they sacks which items were stored and transported in were re-used in countries where Ashkenazi Jews lived among Gentiles who did not keep Passover and kosher laws. Therefore, it was ruled that there could be contamination which would cause accidental eating of some forbidden items. The Sephardic populations did not have these same issues because they lived in warmer climates with different growing seasons which prohibited cross-contamination. Therefore, even today, most Sephardic Jews find it permissible to eat kitniyot. There are many sources on the internet with more details should you be interested. [Please note that I am sharing information about Jewish laws and culture. I’m not stating what I think you should or must do.]
When preparing menus, none of the items above are used amongst the religious Ashkenazi population. I have a wonderful cookbook from which I will be sharing some of my favorite recipes for the Passover/Feast of Unleavened Bread holiday. I plan to post the first recipe on Sunday.