Tinder is easily combustible material used to start a fire. Tinder is a finely divided, open material which will begin to glow under a shower of sparks. Air is gently wafted over the glowing tinder until it bursts into flame. The flaming tinder is used to ignite kindling, which in turn is used to ignite the bulk material, to produce a fire.

Tinder can be made of any flammable substance, as long as it is finely divided and has an open structure.

Wood tinder can be made by carefully shaving thin slivers off a larger piece. Another method which keeps these slivers together, is to make a feather stick. The driest wood, which makes the best tinder, are dead branches that have not fallen to the ground yet.

The gathering of tinder, and perhaps more importantly, its dry storage is one of the most critical aspects of many survival situations.

Examples of tinder include: dry grass, leaves, shaved bark, dandelion head (clock), birch bark, cattail fluff, cattail leaves dry, dry pine needles, fat lighter or fat wood, tinder fungus, punk wood and poplar cotton.

More Info: en.wikipedia.org