There is a wall between Palestine and Israel. The whats, whys, and hows of this wall are highly controversial, but even if you know nothing of the conflicts in these lands, a wall is a wall. If nothing else, it is divisive.
"Send a Message" allows you to send money to the people who are hurt most by this wall; in exchange, they graffiti your message on it. According to their site:
Your text on the Wall reminds Palestinians they have not been forgotten. It helps them keeping hope alive. That's the message you are sending to them, whatever the words are.
*Emily of Ben & Emily, aka "Bemily," dubbed me and Ish (Peter Bartlett) "PB&K"