Chess symbols are part of Unicode. Instead of using images, one can represent chess pieces by symbols that are defined in the Unicode character set. This makes it possible to:
Use figurine algebraic notation, which replaces the letter that stands for a piece by its symbol, e.g. ♘c6 instead of Nc6. This enables the moves to be read independent of language (algebraic notation lists the different names and letter abbreviations of pieces in several languages).
In order to display or print these symbols, one has to have one or more fonts with good Unicode support installed on the computer, and the document (Web page, word processor document, etc.) must use one of these fonts.