The File Transfer Protocol (FTP) is part of the suite of applications provided by the TCP/IP standard. A protocol is a rule, and, as its name indicates, FTP is a set of rules that govern how files are transferred across the Internet using the protocol. Just as HTTP is used to give browsers and servers a common language on the display of web pages, FTP gives servers and clients a common language for transferring files of any kind.
Many companies host FTP servers as a way to share files with customers. For example, a video card manufacturer may make BIOS or driver updates available via FTP so that customers can download the latest updates. For Web Hosting and creating websites, FTP is an indispensable tool. It is via FTP that webmasters transfer their websites from their local hard drive to the web server where the rest of the Internet can now browse to it.
So What is an FTP client? FTP is governed by a set of ASCII commands. While the command set is limited and not difficult to master, most users do not have the time to become familiar with the command set. While I am still very comfortable using the DOS and UNIX command prompts, I much prefer a graphical interface for time and convenience. FTP clients have been written, with very advanced features, to graphically represent FTP commands that happen “behind the scenes”.
Perhaps the most widely used FTP client is Internet Explorer. Most are unaware that Internet Explorer can act as a very basic FTP client by typing the FTP address of the site into the address bar. It provides limited functionality but it is free.
Companies like Globalscape (CuteFTP), CoffeCup, and IPSwitch have been making FTP clients for years that fill the niche. A good FTP client, with advanced features, is well worth the extra investment for a webmaster. The time saved and convenience offered by these programs makes them well worth the small investment.
So, in the end, the basic answer to What is an FTP client is that it is a software program that simplifies the uploading and downloading of files (with some other functionality) to and from a web server.