What is electrolysis? What can be produced with the help of electrolysis?

(N/A) Electrolysis is a process in which a chemical decomposition is produced by passing an electric current through a liquid or solution containing ions.
During this process,electrical energy is converted into chemical energy.
With the help of electrolysis,various substances can be produced,such as:
$1$. Production of metals like $Na$,$Mg$,$Al$ from their fused salts.
$2$. Production of gases like $H_2$ and $O_2$ from water.
$3$. Electroplating of metals (e.g.,coating of $Cu$ or $Ag$).
$4$. Production of chemicals like $NaOH$ and $Cl_2$ via the chlor-alkali process.