Components are mods. mods are modules.
The basic idea of Pagecake is producing a number of mods which are then stuck together on a single website (each one living at a different dir) depending on your needs. The main module is waka
which is a "wiki like html page" creation/editing module.
Look inside the mods
directory for more information about what each module is trying to achieve and if it is a good idea to use it.