What is FTP, and why do I need to provide FTP?

An independent website needs to place all of its files on its web server in order for its visitors to access information based on the website IP. Through FTP, relevant files can be uploaded to servers, and page files can be downloaded from servers, in order to update the website.
Why do merchants need to provide FTP when applying for integration?
Merchant websites need to use FTP to edit or update page files and upload them onto servers, in order to use the Dinpay API.