[Dillo-dev]what does branch mean

Hello everybody: Now I'm studying CCC model of dillo. I see many many modules have their chain functions, whose parameters are similar. When a_Chain_link_new(AInfo...) is called, A new chain is created and a new link is established between the new chain and old chain -- AInfo. Now what confuses me is that what the branch mean? There are only numeric branch,1, 2, 3,... I don't know what they imply. And when a chain function is called, such as a_Cache_ccc(Op, Branch, Dir, Info, Data1, Data2), where does Info come from and what's its meaning? Thank you!