Optics is the theoretical field of light, i.e. the behavior of light. Think: Einstein imagining what it was like to ride on a beam of light, or what would happen to light around a black hole.
Photonics is the applied field of light (photons) and includes lasers, fiber optics, diagnostic imaging, and light sensors (barcode scanners, LiDAR).
Free Space Optical Communications is using light beams for wireless communications. I.e., Wi-Fi with light instead of radio frequencies/waves. (1G-5G Wi-Fi are radio waves. 6G will be too. 7G or 8G might be with light waves). Here, “free space” means wireless, to distinguish it from fiber optics or transmission through a solid medium. Space X Starlink is a well-known example of free space optical communications.
Adaptive Optics is using sensors and mirrors to improve free space optical communications.