Similar to attachments in email, a WordPress attachment refers to an image or file that is uploaded to a post or page editing screen.
WordPress attachments are very similar to email attachments and are uploaded to either a post or page.
Whenever a file or image is uploaded to a post or page, it automatically becomes an attachment of said page.
You can also use forms to enable visitors to upload attachments to send through to your site. For example, using Gravity Forms you can include a ‘upload file’ option and enable visitors to add files to their form submission.
Attachments can come in the form of files such as spreadsheets and documents or media files like image, video or audio files.