I have read that charcoal from a fire can be used to filter water (using a "Three-Tiered Tripod filter"). I have also read that ashes can be used for some other purpose (though I cannot remember).

After a fire has burnt away, what are all that remains? Charcoal? Ash? Anything else? What is the difference and how can they be used? To my ignorant eyes, everything just looks burnt.

Thank you, sincerely,
from Phx, AZ