<input> elements of type
"file" let the user specify one or more files as the value of the
<input> element. The selected files' URLs are listed in the element's
HTMLInputElement.files property. By default, only one file is allowed unless
multiple attribute is set on the element. The element is typically presented as a button and some text describing the currently selected file or files (usually truncated if there's more than one file). Clicking the button displays an appropriate user interface to let the user choose files from the file system, create files, or provide a file from another source such as a camera if the user agent permits it.
For more information on how to access the selected files, please read our Using files from web applications article.