There are two types of unsweetened cocoa powder. Nonalkalized or “natural,” such as Hershey’s, is simply chocolate liquor (nonalcoholic) with most of the cocoa butter (fat) removed after hydraulic pressure. Alkalized cocoa, such as Van Houten, Droste and Bensdorp, is often called Dutch-processed (the formula was created by a Dutchman in the 1800s). Alkalized cocoa powder has a milder taste and is darker and sometimes redder than nonalkalized.
Since most recipes merely call for “cocoa powder,” and since the type of cocoa powder you use does make a difference in the resulting cake’s texture, it is helpful to understand when it is best to use each of them.