Due to the reboot, Sarah Connor has already become a fighter in 1984 in Terminator Genisys.
In serial fictions, the term reboot refers to restart the whole series with a new continuity and discard previous settings.
In Terminator franchise, Terminator Genisys is a reboot of the whole series and sets a stand-alone continuity from other Terminator fictions.
Additionally, the 2009 film Terminator Salvation is a soft reboot as it was regarding as a sequel to Terminator 3: Rise of the Machines while disregarding various setting from the previous installment, such as Cyber Research Systems is removed and Cyberdyne Systems is brought back to the fiction.
The 2019 film Terminator: Dark Fate is a partially reboot as it continues the story directly from Terminator 2: Judgment Day, disregarding the Terminator 3: Rise of the Machines and Terminator Salvation.