What is FTP?
FTP (File Transfer Protocol) is a means by which you may transfer files from one computer to another. For uploading files it is much faster than browser or cPanel based solutions. This process of moving files from your computer to the server is called uploading.
An FTP software program is a must for backing up your site to your local computer. Technically this software is called the FTP Client. We will just refer to as an FTP program. The process of sending your files from the server to your local computer is called downloading. Most likely you have downloaded something before in a browser based environment. FTP is faster.
You will need an FTP address, username and password to connect to the server. Your hosting company will provide this information to you.
The actual use of the software client that you select will vary slightly. I personally use WS_FTP. I am using the older LE version that is not distributed anymore. I have used the same program for over 12 years. It presents the directory on the server and the directory on my local computer in a side by type Explorer window. Here is a link to their site. They have an excellent beginner's tutorial.
If you are using the FREE version of WS_FTP, you will only be able to upload one file at a time, which can be time-consuming. If you have WS_FTP PRO, you will be able to upload complete folders and batches of files at once.
There are many other free and low cost FTP clients out there. Just do a Google search for free +FTP +software