* Electron transfer: One or more electrons are transferred from one reactant to another. The reactant that loses electrons is oxidized, and the reactant that gains electrons is reduced.

* Change in oxidation states: The oxidation states of the atoms involved in the reaction change. Oxidation is an increase in oxidation state, while reduction is a decrease in oxidation state.

* Simultaneous oxidation and reduction: Redox reactions always involve both oxidation and reduction happening simultaneously. This is because the electrons lost by one species are gained by another.

Key points:

* Redox reactions are essential in many chemical processes, including combustion, respiration, and photosynthesis.

* They can be identified by looking for changes in oxidation states of the elements involved.

* The mnemonic "OIL RIG" can help remember the concepts: Oxidation Is Loss of electrons, Reduction Is Gain of electrons.

Let me know if you'd like a specific example of a redox reaction!