In general, we define a disk graph (DG) as the intersection graph of a set of disks in the Euclidean plane. Recently, there has been increasing interest in studying the class of DGs. This primary motivated by its applications which can be found in radio networks, map labeling, and in sensor networks, just to name a few. From another side, DGs have a very simple geometric structure. This motivates the study of theoretical problems. Here we give a short survey on DGs. We briefly discuss coloring, independent set and clique. We include hardness results, main ideas used in approximation and online algorithms, lower and upper bounds. We also mention some open questions.