Because the telnet protocol cannot be used to transfer files, another protocol had to be developed.
ftp can be used to transfer files back and forth between computers. Originally, it was only for UNIX computers, but ftp software is available for Macs, PCs, and other computer systems. On the Mac, you would use a program like Fetch to transfer files.
However, the limitation is that you needed a username and a password on the remote machine before you could connect and download or upload software. This was a problem if you had some data that you wanted to make available to lots of people, you had to give lots of people access to your computer. Something better had to be developed -
ftp became really useful when "anonymous ftp" was developed.
With anonymous ftp, you login with a username of "anonymous" and you can use anything as a password (people usually use their e-mail address)
Once logged in, you can access a limited section of the remote computer.
Now it was possible to access other computers even if you did not have a username and a password on the remote machine.