From the above PDF: The suprabasal cell layer is composed of 5 to 10 layers that appear connected to each other by prickle-like structures. Suprabasal (prickle) cells are polygonal in the lower layer and flattened in the upper layers. They are larger than basal cells and contain a small amount of chromatin in their circular nucleus. The part that gives the appearance of a prickle corresponds to the desmosome (a form of intercellular bridge).

From the PDF below: The basal cell layer is a single layer consisting of basal cells including the epidermal stem cell subpopulation. Basal cells vary in shape from cubic to columnar. They contain basophilic (or darkly staining) cytoplasm and an elliptical nucleus that is rich in chromatin.

They refers to the 4 layers of the skin. Here is an explanation with diagrams http://www.derm-hokudai.jp/shimizu-dermatology/pdf/01-02.pdf