FTP stands for File Transfer Protocol, it can be used to upload and download files from your hosting account. File transfers are made by simply dragging and dropping files from one pane to the other.
With an FTP Client such as FileZilla uploading/downloading a file is really easy. It has lovely features. For example, you can pause and resume when downloading a file. When your Internet connection is slow, it will continue without an interruption. You can download FileZilla by clicking this link
Hostname - The FTP host is what your program uses to find your server. You have several options for your FTP host, and all will work the same. An example of what your hostname is example.com for a domain or ftp.example.com in case you are using a subdomain.
Hosting Details These details refer to the cPanel username and password which can be used to connect to FTP.
Port This is used to connect your account to the server your account is hosted on. For standard FTP make use of port 21.
Directory The main directory for your domain is the public_html. If you are using the cPanel username, make use of "public_html" if your program requires a directory to be specified.