A Geostationary Transfer Orbit (GTO) is a highly elliptical orbit with its lowest point (perigee) in low Earth orbit and its highest point (apogee) at geostationary altitude of 35,786 km. Satellites destined for GEO are first injected into GTO by their launch vehicle, then fire an onboard engine or use electric propulsion at apogee to circularize into their final orbit.
GTO capacity is a key metric for launch vehicles serving the commercial satellite market. The delta-v required for the apogee burn varies depending on the orbital inclination at injection, making equatorial or near-equatorial launch sites advantageous for GTO missions.