>>3870378Focal length means how far is the lens from the rest of the camera.
The amount of stuff that's in focus is Depth of Field.
In general that's controlled by aperture. I.e, f/2.8 will have a narrower DoF, like the top image, while something smaller like f/16 will have a thiccer DoF like the bottom image.
This isn't exactly to scale but you can see the general principle.