[Torhal]

Also, "self" is simply syntactic sugar.

local foo = {}

foo.bar = function(self)
    -- Do something with self.
end

function foo.bar(self)
    -- Do something with self
end

function foo:bar()
    -- Do something with self
end

Dot-notation means you must explicitly pass in the table as 'self'. Colon-notation does so implicitly. The following examples are equivalent:

local baz = foo.bar(foo)
baz = foo:bar()