At any frequency like 2.45 GHz, combining dipole elements into an array can offer a higher gain. Similarly, Yagi antennas , helicals and finally parabolic dishes offer gains exceeding 16-20 dB.
Antenna gain means a higher directivity, or, a narrower beam of the radiating pattern. High-gain antenna must be carefully pointed to the opposite antenna in a radio link. Space around and in front of such antenna must be free, no obstacles, and a direct line of sight is needed to fully use the gain.