What Makes Text Plain
Plain text consists only of readable characters like letters, numbers, spaces, and punctuation marks. It does not include hidden formatting codes or instructions that tell a program how to display the text in special ways. When you open a plain text file, what you see is exactly what is stored in the file, with no hidden layers of information underneath.
Common Uses
Plain text files are used for many purposes in computing. Programmers write source code in plain text files. System administrators use plain text for configuration files and scripts. Plain text is also used for simple documents, notes, logs, and data files that need to be readable across different platforms and programs. Email messages are often sent as plain text to ensure compatibility.
Plain Text vs Formatted Text
Formatted text files, like those created in Microsoft Word or Google Docs, contain extra codes that control how text appears. These files can include fonts, colors, bold text, and images. Plain text files have none of these features. This makes plain text simpler and smaller, but less visually flexible than formatted documents.
Character Encoding
Plain text files must be encoded in a standard format so computers can understand them. ASCII was the original standard and works for basic English text. UTF-8 is a more modern encoding that supports characters from many languages around the world. Most plain text files today use UTF-8 encoding.
Advantages and Limitations
Plain text has significant advantages. It is universal, meaning any device or program can read it without special software. It is durable and will remain readable for decades. It is also secure because it cannot hide malicious code in formatting layers. The main limitation is that plain text cannot display complex layouts, colors, or images like formatted documents can. 
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