[The_Rorschach]

I don't know. . .A story arch, as we used to call them, were storylines that required you to buy other titles that just the main one to figure out what was going on. Like the first Secret Wars run with the Beyonder in the seventies, or X-Tinction Agenda, or any of that.

Storylines were just independant plots that didn't require extra reading to understand. Like Days of Future Past