What is Price Elasticity of Demand?

Firstly let's define Price Elasticity of Demand (PED): PED is the responsiveness of demand to a change in price.

In the real world, Uber is a great example, on a Saturday night demand for Uber often spikes meaning lots of people want to use the service, however there may not be enough cars on the road to suffice demand. As a result Uber has introduced surge charging in which it charges customers more. This increase in price will mean that some people may no longer wish to use Uber and will use taxis or have a friend pick them up instead, allowing those who really need to use Uber to get a car. Uber has quite elastic PED because there are lots of alternatives to using the service in most cities.