How does setmetatable() work and why the metatable is needed in the linked list in lua - lua

Question

I'm learning how Lua's metatables work in OOP, and I am confused of the code I read from the object orientation tutorial on lua-users wiki. Could someone helps to explain the following questions? Thanks.
Question 1:
The wiki's explanation: Here we add a metatable to the class table that has the __call metamethod, which is triggered when a value is called like a function. We make it call the class's constructor, so you don't need the .new when creating instances.
(1)How does the __call get called in the example so the constructor is called?
(2)Does "cls" refer to "MyClass?"
setmetatable(MyClass, {
__call = function (cls, ...)
return cls.new(...)
end,
})
Question 2:
What does {} from the following code refer to?
function MyClass.new(init)
local self = setmetatable({}, MyClass)
self.value = init
return self
end
**Here is the Complete code:
local MyClass = {}
MyClass.__index = MyClass
setmetatable(MyClass, {
__call = function (cls, ...)
return cls.new(...)
end,
})
function MyClass.new(init)
local self = setmetatable({}, MyClass)
self.value = init
return self
end
function MyClass:set_value(newval)
self.value = newval
end
function MyClass:get_value()
return self.value
end
local instance = MyClass(5)
-- do stuff with instance...

Answer 1

Question 1:
setmetatable(MyClass, {
__call = function (cls, ...)
return cls.new(...)
end,
})
This sets MyClass's metatable to a table which defines the __call metamethod. Because of that, you can 'call' MyClass (newObj = MyClass(<args>)). In the metamethod, cls refers to the table that is called, in this case it refers to MyClass.
Question 2:
function MyClass.new(init)
local self = setmetatable({}, MyClass)
self.value = init
return self
end
{} is syntax for a table literal, which creates a new table (an empty one in this case). The MyClass table is set as the metatable for a new table. Then this new table is assigned to self.
More about metatables can be found here: https://www.google.com/?gws_rd=ssl#q=lua+metatables as suggested by Anderson Green in the comments.