What is an arpeggiator?

Hi, I was reading about the General Music Equinox. When I kept on reading about its features, it said it is an arpeggiator. I've been wondering ever since, what is an arpeggiator and what is it for? I would really like some replies if you have the time...because I really want to know what this is.

Well, I look forward to hearing more about the 'arpeggiator' and thanks for replying,
Ryan