Firestarters all work in different ways. A flint and steel method, or a striker and fire rod made from different materials, will work with simple science.
The hardness of the two materials and the contact between the two results in sparks. Your striker needs to be harder than what you are striking it on.
While the firestriker scrapes away a bit of the fire rod, the ripping apart of the material and the friction of the two objects both play a part in shooting small, insanely hot pieces of metal in the direction you want them to go. They stay hot enough in the air (hopefully) to reach your tinder and transfer heat into the dry tinder, resulting in a fire.