Why is a leading comma required when creating an array?

Question

I want to create an array containing arrays of two numbers. Pretty straightforward. However, If I do not provide a leading comma before the first array, it is incorrect. Why

Answer 1

The key to understanding the Array subexpression operator @( ) is the realization that you don't need it to create arrays, instead arrays are created with the Comma operator ,

As a binary operator, the comma creates an array. As a unary operator, the comma creates an array with one member. Place the comma before the member.

$myArray = 1,2,3
$SingleArray = ,1

$xs = (1,2,3), (4,5,6)       # Count: 2    
$ys = (1,2,3),
(4,5,6)                      # Count: 2

Now consider

# A - two expressions, each expression yields one array of size 3
(1,2,3)
(4,5,6)

# B - one expression resulting in an array of two elements
(1,2,3),
(4,5,6)

# C - similar to A except the sizes are 3 and 1 
#     (the second array contains a single element)
(1,2,3)
,(4,5,6)

And the final step is to realize that

in essence, the @(...) operation is syntactic sugar for [array] $(...)

as explained by the PowerShell Team Blog (The link was given by Christopher G. Lewis answer). Although the meaning and limitations of in essence is not entirely clear to me.