Can someone explain making functions to me?

The Roblox Wiki just really confused me and I need someone to explain them to me. Thnx

Usually you shouldn't post things on here without submitting some form of code and asking for help but anyways for basic functions just do this

functionName = function()
	--Code here
end

functionName()

--Or

functionPrint = function(msg)
	print(msg)
end

functionPrint("Hello World!")