Inheritance is a term used in Object Orientated programming that allows one class to inherit properties from another class. The class being inherited is often referred to a super class. The class that inherits a super class is a subclass. Inheritance is great for increasing code reuse.
Let’s say we have a class called Vehicle. Vehicle has many properties such as engineSize, numberOfWheels, and colour. We may also have many methods such as getEngineSize and setNumberOfWheels. If we then make a class called Car which inherits Vehicle, Car will then also have all those properties and methods. We can also add specific properties and method to the Car class which are specific to Car. If we then went on to introduce more classes such as Motorbike and Van, they too could inherit from Vehicle. This means that we can make changes to the Vehcicle class and they’ll be automatically available on the subclasses. This saves us repeating the Vehicle methods on Car, Motorbike, and Van.
A specific application of this in the testing space is the PageObject pattern, commonly used with Selenium WebDriver. A popular approach is to have a base PageObject that manages things like the page being ready to interact with, or a common navigation available on all pages. Then specific pages will inherit the base PageObject giving them access to those waits and the navigation.