ANFO (or AN/FO, for ammonium nitrate/fuel oil) is a widely used bulk industrial explosive mixture.
It consists of 94 percent porous prilled ammonium nitrate (NH4NO3), (AN) that acts as the oxidizing agent and absorbent for the fuel – six percent number 2 fuel oil (FO).
An oxidizing agent (also oxidant, oxidizer or oxidiser) is the element or compound in an oxidation-reduction (redox) reaction that accepts an electron from another species. Because the oxidizing agent is gaining electrons, it is said to have been reduced.
The oxidizing agent itself is reduced, as it is taking electrons onto itself, but the reactant is oxidized by having its electrons taken away by the oxidizing agent. Oxygen is the prime (and eponymous) example among the varied types of oxidizing agents.