Serials usually have a coherent plot that continues from chapter to chapter. Each chapter would have access to each user past performances, giving coherence to the plot. This will help authors to create web or CD-ROM based serials, that are actually much similar in structure to other media serials, like television, but that also give a bigger set of ergodic resources, like the ones available on adventure videogames. One consequence of this is that games have goals. Main goals can be, for example, to rescue a princess or to solve a crime.
Secondary goals are usually things that have to be done in order to accomplish main goals.
For example, finding a key to open a locked door. The game may also impose some secondary goals, like keeping the major popularity high, or administrating with care the city funds. The author may design the program so its closure would be a direct consequence of the user's actions. The story would end if the character dies or wins. Another option would be to have a limited time, like in theater plays or movies.