Dumb question - difference between Dodge and Plymouth

In the earlier years each division of Chrysler had there own V8 engines that you might only find in one or the other car lines Chrysler start building the first generation Hemi's in 331,354,392. Desoto had the 276,291,330,341,345. Dodge built them as 241,270,315,325,426.
The Plymouth division never utilized a Hemi until the 426 in 64. So there were differences in the divisions.