A Gas Giant is a Giant Planet such as Jupiter or Saturn: massive and mostly gas, i.e., Hydrogen (H) and Helium (He). Many discovered Extra Solar Planets are gas giants which is to be expected because larger planets are easier to detect.
Extra Solar Planet
GJ 1214 b
Gemini Planet Imager (GPI)
Hot Jupiter (HJ)
Keck Planet Imager And Characterizer (KPIC)