This is a well-written article which uses a geometric approach in the study of real quadratic planar differential systems, i.e., systems of two first-order quadratic ordinary differential equations with real coefficients that have a vector field. The interest is in the global theory. Probably the most famous open problem related to this study is Hilbert's 16th problem which seeks to determine the maximum number of limit cycles which appear for such systems and their possible relative positions in the plane. The principal aim of this work is to seek geometric clarification on results and methods such as the isocline method and the role of rotation parameters amongst other things.