Howdy amd welcome to DC!!
Crisco is simply a brand of solid vegetable shortening. It resembles lard but is not made from animal fat. If dietary concerns about saturated fat is not an issue, I would substitute lard.
Buttermilk, traditionally, was a term used for the liquid left behind after churning whole milk to make butter. Cultured buttermilk, which is what is found in most supermarkets, is made by adding lactic acid bacteria to milk. Without getting too technical, this raises the Ph of the milk and causes the milk clabber, which is why it is thicker than whole milk.
Baking Soda and Baking Powder are leavening agents (Yeast is a leavening agent, too) added to flour to cause, in this case, cake to rise.
Cocoa powder is a dried, granulated form of chocolate.
Cream of Tartar is made from the sediment produced during wine production.
Tartartic acid is found in grapes. Added to egg whites to help stablize and give more volume when beaten. It is also used to produce a creamier texture in frostings and candy.
I hope this will help a little.
I am sure that there are others here with more in depth information.
Again, Welcome to DC!