Its scientific name is Salvia Apiana; it comes from the Latin salvare - to heal. In Celtic Europe, druids would use it in order to increase their wisdom and during healing and protection rituals. Many Native American cultures from the west coast of the US would also make use of the plant to purify body and mind; leaves were burnt and the resulting white smoke served to bless and cleanse people as well as objects. Finally, California white sage is a well-known medicinal plant.
How to use it: you can burn directly the white sage smudge bundle by lighting one end. If you are thinking of cleansing a room or the place you work in, it is recommended to have a good ventilation. Another way of proceeding is to burn the leaves separately in a bowl with a high resistance to heat, such as a sea shell, as Native American would do.