In this paper, a technical review on gap-coupled microstrip antennas is presented. The gap-coupled microstrip antennas give a large bandwidth as compared to the conventional microstrip antennas. The method of bandwidth enhancement using gap-coupled microstrip antennas has been elaborated. The gap-coupled microstrip antennas also produce two resonances. The dual frequency operation of the gap-coupled microstrip antenna is also described. A research overview of gap-coupled microstrip antennas, challenges, types of gap-coupled microstrip antennas as well as numerical methods of calculating various parameters of the gap-coupled microstrip antennas are discussed in this paper.