A back button is a basic control used by a variety of technologies. In a Web browser, a back button allows an end user to navigate to a previously viewed Web page. A back button also is a feature of smartphone software and other consumer oriented technologies.
Techopedia explains Back Button
Considering the role of object-oriented design (OOD) in modern programming is helpful when trying to understand back button functionality. Often represented by a set of generic visual icons, a back button is a control object that programmers code into applications. In alternative technologies like the Amazon Kindle and other e-readers, a back button is represented by code linked to a physical button on a device shell, versus a coded object and icon.
A back button also represents the principle of successive pages as a key Web design component. This is a technology principle utilized by many areas of IT, such as Apple's early HyperCard program. In these and similar technologies, a complete application is developed and presented to end users as a set of pages or cards, and a back button that is used a critical navigation tool.
It is likely that the back button will continue to be a popular device and application control, as most end users are familiar with the concept of linked pages.