Originally Posted by: Ybwhat is the use of praticing appeggio?

Ditto what Sixpicker & others said...
And I would also add, that arpeggios are just another tool of expression for you to use in your playing. People will often tend to associate arps with the whole "shredder" genre....but in all honesty, having even the most basic grasp of the concept of arpeggios is a very useful tool for you to have at your disposal, regardless of the style you play.
Arpeggios really do get a bit of a bad rap, because of the overuse of them in the rock/metal/shredder genres as a means of launching a bazillion notes at the listener with sweep-picking & what not. But beyond the cliched shred applications, they are extremely useful for working your way around the neck & linking up various scale positions up & down the fretboard, etc...There's really just too many applications to list in a quick, short answer. But suffice it to say, that they are a very useful tool for nearly any style & well worth the time that you put into them.

Don