Описание тега multer
Multer is a node.js component used to handle multipart/form-data uploads.
Multer is a node.js middleware for handling multipart/form-data, which is primarily used for uploading files. It is written on top of busboy for maximum efficiency.
Multer will not process any form which is not multipart (multipart/form-data).
Github repo https://github.com/expressjs/multer.
Github repo busboy