A terminal is an easier way to manage a UNIX system.
However... the term "easier" relies on a huge amount of experience of working with a similar system. For example... If you put a windows user on a mac machine he would have to search for ways to cut,paste, change resolution etc... You on the other hand already know how to do this.
BUT in UNIX there are no such things as a good tutorial. We ALL have to go the hard way I´m afraid.
The terminal is a non-graphical interface to the system. Keep in mind that non-graphical is a LOT faster than graphical. You can easily see what´s going on inside the system. Remember the movie matrix? Picture the real world as the GUI. The nice colors, the birds singing, people laughing crying etc... But if you took away all the graphical stuff, it would be just text. One command linking to another. If you went to see a close friend a few blocks away, you would have to get your clothes on, locking your apartment, take the buss etc. But in "terminal-mode" you could just "type" it. "Get clothes. Go to buss." etc... Do you understand me?
But to be able to use the terminal you would have to know all (or almost all) the strange commands. And it´s almost easier to get a Phd in philosophy than learning all the commands in UNIX. (almost)
Summary: The terminal is a way to communicate to the system without the use of graphic.