The weapon worked by sending a stream of energy through an outgoing wormhole, the device was capable of storing energy in the gates capacitors. However, if too much is stored, the gate was capable of exploding in a blast resulting in two to three thousand megatons, enough to wipe out all life on a planet the size of Earth.
The destroyer weapon was a large structure located on a planet which contained a ring of smaller obelisks with a central structure firing the energy beam into the Stargate. The edges of the structure are shielded by the obelisks preventing entry through the open areas, however, there was a doorway allowing individuals to pass through unimpeded.
This device was once used by Anubis to destroy Earth. His attempt did destroy the gate, but with the use of the X-302 spacecraft, they were able to transport the Stargate into space where it exploded several light-years away. Because there was a second Stargate on Earth, Earth still had a Stargate.