Oxidation-reduction (redox) reactions involve the transfer of electrons from a reducing agent to an oxidizing agent. 

There are mnemonic devices to help us remember what oxidation and reduction is.

1. OIL RIG - Oxidation is losing (electrons); Reduction is gaining (electrons)

2. LEO the lion says GER - Loss (of) electrons (is) oxidation; Gain (of) electrons (is) reduction

Other terms to note are:

1. Oxidizing agent - the species gaining electrons; the species undergoing reduction; the oxidizing agent oxidizes another species

2. Reducing agent - the species losing electrons; the species undergoing oxidation; the reducing agent reduces another species

Think about a travel agent. A travel agent is someone you go to to set up travel plans. The travel agent is not doing the travelling… you are. The travel agent enables you to travel. An oxidizing agent allows something else to be oxidized. The oxidizing agent undergoes reduction to do this. Similar logic applies to the reducing agent.

Oxidation numbers, also known as oxidation states, help determine what is being reduced and oxidized in a chemical reaction. Oxidation numbers are assigned to individual atoms to indicate the apparent charge they would possess if the compound were composed of purely ionic bonds. 

Rules for assigning oxidation numbers:

Oxidation numbers play a crucial role in balancing redox equations, predicting reaction products, and understanding the reactivity and stability of compounds.