You might consider using a soil sampler, such as Soil Sleuth, to avoid damaging your nails. It is plastic and costs about $10 and never wears out or needs new batteries.
DIRECT sun is a location where the sun's rays fall directly on the leaves of the plant at some point during the day. Of course, the sun moves so direct sun at one point might not be direct sun later in the day. Some plants may need direct sun for most of the day while others may not tolerate more than a couple of hours of direct sun.
INDIRECT sun is anything beyond the reach of the sun's rays during the day. "Bright" indirect sun is just barely beyond the reach of the sun's rays, usually no more than a few feet from a sunny window. However, because light intensity drops off dramatically with every foot of distance from the window, once a plant gets more than about 6-8 feet from the window, even low light plants will struggle.
One rule of thumb for minimum light for any plant is that the light has to be adequate to read newsprint comfortably in that location at any time during the day light hours.
Hope that helps.
