Aperture Control...

Okay Blippers, someone explain to me please the affect of aperture on focal distance/depth of field.

I have this habit of always wanting to know what every button on a gadget/product I own does. My new camera has a depth of field preview button which when pressed whirrs something and adjusts the image in the view finder.

Oh, and can the aperture setting be adjusted to help close up shots, if so, which way?

This was just a wee test with stacks of Bethany's blocks at varying distances.

Ta.