Apophis' training planet was a settlement established by Apophis and was used to train human underlings for a subtle infiltration of Earth. Half would be armed with Tau'ri weapons, while another group would wear Jaffa armor and carry staff weapons.
The settlement was made to appear like an average Earth military installation, with crew quarters, an armory and equipment tent, which were required to sustain the operation. The trainees battled with Intar weapons for training, before switching to real weapons, which were stored in a cave.
When the trainees learned of Apophis' death in 1999, their leader Rophiapgisy encouraged them to abandon the camp and return to their home worlds. (SG1: "Rules of Engagement")