Whitespace characters are special characters in text that do not produce visible marks but create space between words and elements. Common examples include spaces, tabs, and newline characters. They help organize text, making it easier to read and understand by separating words, lines, and paragraphs. In programming and markup languages, such as HTML and Python, whitespace characters play a crucial role in formatting code and improving readability. They can also affect how text is displayed in user interfaces and how data is processed, as some programming languages treat them as significant while others ignore them.