[video=youtube;l29wCKkQpMg]https://www.youtube.com/watch?v=l29wCKkQpMg[/video]
What if find amazing is that the bright bit at the bottom of the image is both the front and the back of the black holes accretion disk, it's on the other side of the back hole. Gravity is so strong it bends the light right round to the front. Likewise the dark spot in the middle is both the front and the back of the event horizon.
Great explanation here
[video=youtube;zUyH3XhpLTo]https://www.youtube.com/watch?v=zUyH3XhpLTo[/video]