Much of the text that is used to express content on contemporary websites is categorized as belonging to the OpenType format. This is primarily responsible for digital text's capacity to be scaled to larger sizes without a loss in sharpness and clarity, and its use has been standardized between Windows PCs and Macs so that many commonly used fonts can be stored in files that would work on either platform.
Font files contain more information than just stylistic designs for every letter and number that appears on a standard keyboard, however. For example, they support allowing sequences of specific letters to be displayed as though each of the letters is "connected" or "interacting" stylistically. Many spoken languages' accompanying writing systems are dependent on this functionality because they involve ligatures, a common example of which is a symbol that resembles the letters "A" and "E" conjoined together. A typist rapidly producing web content might rather type those letters separately and enclose them in the compatible CSS syntax than look for and carefully insert the intended symbol's Unicode equivalent.
Even in the context of the Latin alphabet, this functionality regarding ligatures can be useful because it allows each occurrence of a set of specific letters to portray the two letters as stylistically influencing each other for the sake of enhancing a website's sense of branding. Two letters can even be portrayed as symmetrical halves of a symbol that bears no resemblance to the letters whatsoever, but highlighting it with the mouse cursor would reveal that it is still counted as separate "letters" internally.
Many font files also contain their own adjustable "settings" that allow web authors to present text in subtle font variations that respect the likelihood that viewers may have a harder time visually parsing text at certain scales. If certain sequences of letters occurring throughout a block of text look either overly cramped or spread too far apart from each other, for example, the CSS syntax being used to stylize that text can include specific definitions for the text's "kerning." This syntax might not work on other font files. For more information click here https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Fonts/OpenType_fonts_guide.