Windows views text files as just another file type, but to SUSE Linux, they can be essential system components that make the system work. Configuration files are stored as plain text, and program documentation is also stored as text. This is clearly different from Windows, where it's very likely any information you're supposed to read will be contained in a Windows Help file, a rich text format (RTF) file, or even a Microsoft Word document.
Because of the importance of text files, the shell includes several commands that let you display, edit, and otherwise manipulate text files in various ways. Learning to use the shell, and therefore learning how to administer your SUSE Linux system, involves having a good understanding of these text tools. You'll use text tools for editing configuration files and viewing log files, as just two examples.