A hydrocarbon or another organic molecule is frequently used.
Pure hydrogen gas is the simplest fuel available.
Oxidizer: The electron-accepting molecule is known as an oxidizer.
Oxidizer turns out that burning necessitates oxidation, or the donation of electrons, by the fuel. So we'll need something to accept the electrons, which will be the oxidizer, which will be reduced later.
Because oxygen is electronegative, it prefers to take electrons, it is an excellent oxidant
Only fluorine is more electronegative, and fluorine is an excellent oxidizer: blast fluorine gas at almost any solid, and it will erupt in flames.