foreground/background depth

The foreground is the sign.  I tried to make the sign more in focus
by making it a lot sharper than the background 

The plants are the foreground.  The brick wall is the background
The plants are very bright and colorful, while the background is a duller color.
The contrast makes the eye drawn to the plants first.  

The light is sharper, while the background is blurry.  The light is the foreground.

I tried to contrast the light metal bars against the dark stairs.
The bars are the foreground the stairs and wall are the background.