This article explains what RTF files are and how they differ from other text documents. It also explains how to open an RTF file or convert it to another format, such as PDF or DOCX.
A file with the .RTF extension is a Rich Text Format file. It differs from a regular text file in that it can contain formatting such as bold and italics, plus various fonts and images.
RTF files are useful because many programs support them. This means that you can create one using a macOS program, for example, and then open the same file in Windows or Linux and it will essentially look the same.
The easiest way to open an RTF file in Windows is to use WordPad, since it comes pre-installed. If you're using a Mac, Apple TextEdit or Apple Pages will work.