What is "scritching" your scalp?

When I scritch, I gently scratch my scalp with my fingernails before I brush at night.  Sometimes bits of scalp release (gross), sometimes I find little blemishes, sometimes I find sore hair follicles maybe because I pulled my ponytail too tight?  Maybe I missed brushing the area?

I don't do it long, I use both hands and scritch from my crown to the outer edges like I'm drawing lines like a knit cap, does that make sense?  I only do it at night and it tells me where to brush or massage more, and where to add aloe vera gel to fix dry spots. 

I must also say that my brushed are generally pretty clean until close to wash time.