In plain emacs you can do 
 - 'C-h m' to show help for current major and minor modes and their commands
 - 'C-h b' to show all key bindings
 -  after prefix command 'C-h' to show bindings starting with prefix

If you use which-key it will display the available keybindings on minibuffer and 'C-h n' 'C-h p' will be used to change pages on minibuffer, to show bindings for prefix like plain emacs you will need 'C-h h'