Pyrography is burning designs into certain materials like wood, using some kind of heated instrument to create decorative burn marks. Today, this is done mostly by using specialized burning or pyrography tools.
Pyrography can be traced back to ancient times in places like Egypt and certain places in Africa, where designs were created by using the charred remains of fires or burning sticks.
Many of the wood burner sets come with stencils you can use to apply various designs. You can also simply go freehand and design your own image. The third option is to transfer your own image onto the wood surface.
Once the burning pen is hot enough, you can then start burning your image into the wood. When attempting even lines, try to keep even pressure as you go.
Facing a black wood surface, even if it has a design on it, can seem a bit daunting. How do you burn in the design? Going on a workshop, looking at some YouTube tutorials, or purchasing a good book can help.
Pressure-treated wood should not be burned, as it has been in contact with chemicals and might be safe for construction, but if you are going to be burning into the surface, it will become hazardous.