In the 18th century, Rowena created and used this spell to kill demons. When she decided to rebuild her power base, she started by recruiting girls from a demonic brothel and used the spell to kill Raul. This drew the attention of Crowley, Sam and Dean Winchester with the latter two identifying her as she was the only practitioner of it.
The website Sam was looking at identified the spell's use as "To Bind and Purge" which is what the spell's name translates to.
The spell requires the targeted demon to hold a hex bag full of unknown ingredients, with a sigil inscribed in it. Shortly afterwards, the demon will begin to violently cough itself up out of its vessel, and in its smoke form, will start to liquefy, and eventually die.
The spell is not able to kill the strongest demons - its affect on Crowley was minimal, and wasn't able to kill him. He was even able to burn the hex bag and disable the spell.