We revisit the well-known Tkach and Chraplyvy (T-C) diagram of feedback regimes in semiconductor lasers. Our aim is twofold: first, extending the classification of feedback effects in the T-C diagram to short and long external cavities, and to coherent and incoherent interactions; second and more important, identifying in the diagram feedback phenomena that have been meanwhile studied and developed to noteworthy applications, namely, self-mixing, period-1 and multiperiodicity, intermittency and chaos. We complement the feedback diagram with application regions, so as to describe not only feedback effects detrimental to a laser used as the transmitter of an optical link, but also feedback effects in the weak and strong regime of interaction, developed into applications for instrumentation and communications in recent years.