LavaBurst creates an icon, by default to the right of the centre of the screen, when a shaman's Lava Burst ability is not on cooldown.
This can help shamans to maximise their DPS by assisting them in continually casting Lava Burst whenever available, especially helpful since the introduction of the Lava Surge talent, which resets the cooldown.
Check out the LavaBurst Options AddOn if you would like to able to customise the AddOn to function for particular talent trees if you have dual talent spec, and move it into your desired position with the lock/unlock and advanced positioning features.