Emacs Helm: what actions can I do in a helm buffer?

I have 2 questions:

In a helm buffer like helm mini or helm ag, there are usually too much candidates. In evil mode I can use C-d or C-u to scroll down or up. Can I do such things in helm buffer?
Sometimes when I enter a file path/name, there is only a default one in the buffer but not the one I entered. Whenever I hit enter the default path/file will be visit. What actions can I do in the input bar (where you input characters)?

Would you please provide the document describing these kind of keymaps? I can't find them because I don't what's my question :(

Solution

If you are using spacemacs, try M-x describe-keymap helm-map, it's bound to SPC h d K.

Sadly emacs itself doesn't have such a nice describe-keymap function. In this case you may either:

copy describe-keymap from spacemacs
use describe-bindings (it's not so smooth to read and misses some keymaps)
C-h v helm-map to browse the keymap as a variable (hard to read because the keys are in the form of something like unicode code points, but if you config all your key bindings yourself without framework-defaults, this is fine for "what's my bindings?" and debugging)