Question

How does a decomposition reaction differ from other types of reactions?

Answer 1

Decomposition has only one reactant whereas other reactions have two reactants.

An example of a decomposition reaction is shown below:
2NaCl(s) -> 2Na(s) + `Cl_2`

Here is a video which shows the chemical reaction that takes place when baking soda is heated. It is another example of a decomposition. The video discusses the chemical equation for the process and also shows you how to balance the equation.

Video from: Noel Pauller

Sufficient coverage, not too complicated here: http://study.com/academy/lesson/decomposition-reaction-definition-examples-quiz.html