Capistrano Callback Order and Recipe Brief Explanations
I’m not familiar with capistrano at all, I kind of use it in daily base but what I’m capable of is just the one major command: ca deploy, heh that’s all I got.
Capistrano Callback Order
If you like me always get confused by the callback orders, image is really gonna help you out.

Capistrano Task explanation
Capistrano recipes: deploy is brief explanations of each task, same in the source code I think, highly recommend you go through them once.
Another good resource is capistrano recipes source code
task :update do
transaction do
update_code
create_symlink
end
end
Like this :update task is easy to guess: run update_code and create_symlink in a transaction.