What is the difference between redox reactions and oxidation and reduction reactions ?

Oxidation is loss of electrons.

Example: 

Mg → Mg²⁺ + 2e

Here, magneisum has oxidised by loss of electrons to form magnesium cation.

 

Reduction is gain of electrons.

Example:

Mg²⁺ + 2e  → Mg 

Here, magnesium cation got reduced to magnesium metal.

 

Redox means reduction and oxidation taking place in the same reaction then it is called as redox reaction.

Example:

 

Consider the reaction between zinc metal and hydrochloric acid.

Zn(s) + 2 HCl(aq) → ZnCl²(aq) + H²(g)

If this reaction where broken down to the ion level:

Zn(s) + 2 H⁺(aq) + 2 Cl-(aq) → Zn²⁺(aq) + 2 Cl^-(aq) + 2 H₂(g)

Zinc atom loses two electrons to become a Zn²⁺ ion so undergo oxidation, 

Hydrogen ions are gaining electrons and bonding together to form dihydrogen gas. So undergo reduction.

Hence thi reaction is redox reaction.