Ferro is short for Ferrocerium which is the alloy from which ferro rods are made. When you strike the ferro rod, tiny particles flake off and ignite when they hit oxygen. These sparks can reach temperatures of nearly 5500F. Ferrocerium is used in strikers for welding and cutting torches. It is also used as an ignition source for lighters. The alloy was invented in 1903 by combining Iron and Cerium.
Ferro rods are commonly confused with the flint and steel method of starting fire. Ferro rods are in no way related to rock flint, and they actually work in opposite ways. With a ferro rod, it is tiny particles of the ferro rod that ignite at a low temperature. With flint and steel, it is actually tiny particles of steel that ignite, not the flint. While you can find flint in the wild and start a fire with it, ferro rods are generally considered to be more reliable.
There are dozens of different ways to start a fire in the wilderness. I always have a ferro rod as an option when I am on a survival challenge. Friction fire can get the job done, but it can be incredibly time consuming. Finding the right types of wood can take days of trial and error in some cases. Using a lens to start a fire can work well, but only if you have a sunny day and no trees blocking the sun.
Piston fire starters and matches are just too unpredictable in wilderness conditions. If there is any moisture present, they can be difficult. I do like to keep lighters with me as they can be helpful if you are wet and need to warm up quickly.
However, despite all of these other good options I still feel that the ferro rod is the most reliable. If a lighter gets wet, there is a chance that it could be ruined or could need to dry out before it will light up again. A ferro rod will always give you the opportunity to build a fire when you need one.
Want to learn how to use a Ferro rod properly? Here's an in-depth explanation
Want to get your own Ferro Rod? Here's your best option