Lua/wow api help

[yoyoyo]

I'm learning LUA for wow addon's and it say's to look at samples so I downloaded a very simple addon and looked at the code this was it:

local frame = CreateFrame("FRAME");
frame:RegisterEvent("ADDON_LOADED");
frame:RegisterEvent("DUEL_REQUESTED");


function frame:print(msg)
	DEFAULT_CHAT_FRAME:AddMessage(msg)
end


function frame:OnEvent(event, arg1)
	if event == "ADDON_LOADED" and arg1 == "DuelCancel" then
		if duelcancelbool == nil then
			duelcancelbool = "on";
		end
	elseif event == "DUEL_REQUESTED" then
		if duelcancelbool == "on" then
			CancelDuel();
		end
	end
end


frame:SetScript("OnEvent", frame.OnEvent);
SLASH_DUELCANCEL1 = "/duelcancel";


function SlashCmdList.DUELCANCEL(msg)
	if msg ~= nil then
		msg = string.lower(msg);
	end
	if msg == "on" then
		print("DuelCancel: on");
		duelcancelbool = "on";
	elseif msg == "off" then
		print("DuelCancel: off");
		duelcancelbool = "off";
	else
		if duelcancelbool == "on" then
			print("DuelCancel: ".. duelcancelbool);
		else
			print("DuelCancel: ".. duelcancelbool);
		end
		print("Type /duelcancel off or on to change");		
	end
end

Let me type out what I believe its does.
Assigns a local variable called frame which is equal to CreateFrame("FRAME")
Then it tells the frame variable to register a event when the addon is loaded and also an event when a duel is requested.
Then it creates a function called framerint(msg) .... ? that tells DEFAULT_CHAT_FRAME to add a message with the msg variable? and thats where I get confused...

what assigns the "msg" variable? why is the function named "framerint(msg)"? I tried reading the wow api pages on wow wiki but holy shit.. that just sends me everywhere... something that would help me alot would be if you could tell me what the : after the variable does I went threw the entire LUA handbook and didn't find anything there about the colon... this is a simple addon and I don't understand it ... +rep for help... even links are good to get me started. I watched a whole video on lua tutorial and read the handbook.

[hp94]

What you're looking at is Widget API. There's a good page on WoWWiki for that that explains it. In the 'msg' case, msg is the parameter taken in to the function. For the rest, try reading lua-users wiki: Inheritance Tutorial .