Someone may have a better explaination but here's mine..
The ink pad is applied "direct to paper" to create backgrounds etc. The "new" (to stampin up anyway) petal point chalk pads are perfect for this as they are small enough to "stamp" onto paper to create backgrounds.
Here's a link with some examples
http://www.rubberstampsclub.com/tips/directtopaper.html
And here's a description from
http://kimstamps.com/stech.htm
DIRECT TO PAPER
Apply colors directly to paper with Cat’s Eye, Petal Point, Colorbox, Paintbox, or Option Plates by gently rubbing the pad onto the paper. You can use the entire sponge surface or part of it (tip or edge). The movement of your hand will create a texture or pattern. Try different movements, never press or pull too hard. Reink often to avoid damaging the foam pad. This can create a beautiful background. Use 2-3 colors.
Stamp all the images with darker color ink. At this point you have 2 options:
Let it dry as is & consider your artwork finished.
Emboss the entire surface with Clear powder for an enameled effect.
HTH!
Ashley