The beings known in Common as the “True Gods” are called “Tiravita” by the elves, which literally translates as “lifebringers.” Almost nothing is known about them other than mythological stories of them arriving in Valwyr with swords made out of stars and armor forged from the heat of the sun. They warred with the Walking Gods and the people in Valwyr for a length of time unknown, but eventually drove the Walking Gods off (or killed them, depending on which story you listen to) and established the elves as the prominent force in Valwyr.
The only other thing we know about them is that they no longer exist on Valwyr, and our current pantheon has no relation to either the Walking Gods or True Gods. In fact, the Gods we worship today existed before Recorded History as well.
So why do we call them the True Gods? Because to the elves, they are, and always will be, even while they worship Corellon Larethian as their patron god. The Walking Gods brought life and earth to Valwyr, and the True Gods brought order, justice, and intelligence, all things the elves value.