TM06 is a TM that teaches the move Toxic. Toxic is a 90% accuracy Poison-type move that inflicts the badly poisoned status on the target. The badly poisoned status will do an increasing amount of damage to the victim each turn, starting at 1/16th of the Pokémon's maximum HP, and increasing by 1/16th each turn. This counter is reset upon switching out.
Due to a bug in version 2.2.1 of Pixelmon, when you swap out a Pokémon who is affected from poison (or sleep, paralysis, confusion, or freeze), the status ailment the Pokémon should have will sometimes be replaced with a burn status effect. This bug is particularly annoying because the burn status halves the attack stat and does damage equivalent to 1/8 of your Pokémon's max health each turn.