How to understand android display framework flow?

I have some naive question, as I have never worked with android as a whole. I am trying to undestand display framework of android.

Above is a picture that I saw in android display framework. I want to understand how this flow works.

1.After status bar how can a hardware like GPU be there?

2.How can GPU be inside of surfaceflinger, while all the hardwares are only accessible through kernel drivers?

3.Is graphics HAL different than display HAL or both are same?

Thanks.