Surface-tethered polymers, or "polymer brushes", are emerging as key elements in the context of regulating the surface characteristics of materials. Their properties, such as biocompatibility, antifouling, colloidal stability, wettability, and corrosion resistance, play a vital role in ascertaining their potential applications. The availability of straightforward procedures for polymer brush synthesis, which are applicable to a wide range of monomers and are adaptable to a range of substrates, is a clear advantage over other surface-modification strategies. Herein, the important advancements that are pertinent to the fabrication of polymer brushes are outlined. Furthermore, an exhaustive up-to-date overview of the developments in different application domains, including smart drug-delivery systems, biosensing, antifouling, stimuli-responsive surfaces, and ion-conducting membranes, that benefit from the developments in the field of polymer brushes, is presented.