1.3.2 I can identify file types based on their extension

File names have two parts; the file's name, then a period followed by the extension (suffix). The extension is a three- or four-letter abbreviation that signifies the file type. For example, in letter.docx the filename is a letter and the extension is docx. Extensions are important because they tell your computer what icon to use for the file, and what application can open the file. For example, the doc extension tells your computer that the file is a Microsoft Word file.