[Click] help with the Discard element

[David Fusté]

Hi,
I'm novice in Click and I have simple questions. I'm working with click 
in user level mode.

This is my config file:

% cat prova.click
FromDevice(wlan0)->Print(ok)->Discard;
%

When I run it, obviously, click starts to capture packets. Then, when I 
open the browser, click starts to print the packets.
My first question is: why does the browser correctly load the web pages? 
i.e. why doesn't click discard the packets?
And in relation to this, since click doesn't discard packets and it pass 
them to linux, what's the meaning of the ToHost(DEVNAME) element?
    
And it isn't all, if I run this other config file:

% cat prova2.click
FromDevice(wlan0)->Print(ok)->ToHost(wlan0);
% click prova2.click
prova2.click:1: While initializing 'ToHost at 3 :: ToHost':
 ToHost(wlan0) requires an initialized FromHost with the same dev_name
Router could not be initialized!
%

why does ToHost element need a FromHost element? I only want to capture 
packets from device to linux, not from linux to device.
Moreover, there isn't a FromHost element in user level mode! Why does 
ToHost user level element want a FromHost kernel element? It isn't possible.

I don't know where I am wrong. Help me please.
Thank you!

David