Why do Computers Use Binary

While watching this video, I have learned several new things. One new thing I have learned was that the way the sound goes through your headphones is called analog signal. Another thing I learned was that the binary method numbers are called "Base-n Numerals". Lastly I had learned this system helps computers in multiple ways. One thing I don't really understand is how quickly people do this activity. Another thing I don't really understand is how you can do large numbers in this binary system. One thing I would like to know more about is why this system was created.