Many-item pointers test example introduces new feature without explanation

[jeramyRR]

Hi,
Thank you for this guide! it's been a joy to read so far.

I ran into a new feature in the Many-item Pointers section that doesn't have an explanation of what's going on.

test "many-item pointers" {
    var buffer: [100]u8 = [_]u8{1} ** 100;
    ...
}

What is going on with the rhs of var buffer: [100]u8 = [_]u8{1} ** 100;?

Thanks,
Jeramy