question about a code...

[MrPolite]

BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);

            int stride = bmData.Stride;
            System.IntPtr Scan0 = bmData.Scan0;

            unsafe
            {
                byte * p = (byte *)(void *)Scan0;
.
.
. 

what does that red line exactly do? I know it declares a pointer p, but what does the "(void *)" on the right side of the equal sign do?

also, it accesses p like an array (ie, p[0] ) why is that?