INDEED
Teal'c is a Jaffa from the planet Tul'ac. In the decades before the
events of Stargate SG-1, the Goa'uld System Lord Cronus executed
Teal'c's father (Cronus' First Prime, the most senior Jaffa rank)
for retreating during a battle that could not be won. In the hopes
to avenge his father's death one day, Teal'c joined the armies of
the rival System Lord Apophis. Under the direction of Apophis'
then-First Prime, Bra'tac, Teal'c learned the ways of a warrior and
rose in the ranks to become Apophis's new First Prime. His
interaction with Bra'tac and his own personal experiences led him
to doubt the divinity of the Goa'uld.
When the SG-1 team is captured on Tul'ac in the pilot episode of
Stargate SG-1, Teal'c defects from Apophis and joins the SG-1 team.
He believes this to be an opportunity to eventually defeat the
Goa'uld and bring freedom to all Jaffa. Teal'c finds a home at
Stargate Command (SGC) on Earth and occasionally visits his wife
Drey'auc and his young son Rya'c on Tul'ac. SG-1 joins forces with
Bra'tac in many missions against Apophis in the next four seasons.
Teal'c's integrity in the team is tested after he kills Daniel's
wife Sha're in season 3's "Forever in a Day" to stop her torture of
Daniel. After SG-1 succeeds in killing Apophis in the season 5
premiere, "Enemies", Tul'ac becomes a free planet.