What is the difference between arpeggio and a glissando?

A glissando is the 'gliding' from one pitch to another. In other Words moving from one or a series of notes written after each other. An arpeggio is the 'rolling' of a chord. Sometimes this is done to improve chordal spacing. For example it is extremely difficult if not impossible to play the a below middle C, middle C and e together. To make it easier for the pianist this chord is 'rolled' or arpeggiated, although it is still written on top of each other (a, md. c, e).