What do oxidation reduction reactions involve?
Oxidation reduction reactions (redox) involve elements whose oxidation state (charge) changes during a reaction.
Here is an example of a redox reaction:
Mg has no charge before the reaction, after it has a charge of +2 - meaning it was oxidized.
Iron goes from a +3 charge before the reaction to a an oxidation state of 0 after the reaction - meaning it was reduced (reduced charge due to addition of electrons).
If no elements in a reaction change oxidation state (for example: double replacement reaction) the reaction is not a redox reaction.
Here is another example of a redox reaction with video of a demonstration of the reaction...
Hope this helps.