A file is an object on a computer that stores data, information, settings, or commands used with a computer program. It is a resource for recording data on a computer storage device, primarily identified by its filename. Files can be shared with and transferred between computers and mobile devices via removable media, networks, or the Internet. Different types of computer files are designed for different purposes, such as storing an image, a written message, a video, a program, or any wide variety of other kinds of data. Certain files can store multiple data types at once. By using computer programs, a person can open, read, change, save, and close a computer file. Computer files may be reopened, modified, and copied an arbitrary number of times. Files are typically organized in a file system, which tracks file locations on the disk and enables user access.

There are three types of files on a computer: application files, data files, and system files. Application files are used to run software programs, data files contain information created by a user, and system files are used by the operating system to run the computer. Folders are used to organize files and can contain one or more files. Folders can also contain other folders, and there can be many levels of folders within folders. Folders provide a method for organizing files much like a manila file folder contains paper documents in a file cabinet. Files are identified by a short "extension" following a period at the end of their name. For example, ABC.JPG is a JPEG image, ABC.DOC is a Microsoft Word document file, and ABC.EXE is an executable application in Windows.