Espressivo? what is it?

This forum seems very quiet. I find in my paid for HAlion Symphone orchestra - the one with Cubase 6 there is an espressivo option, but no exaplanation in the manual about what it is, just how to assign them.

What is it?

Espressivo patches have more intense vibrato.

But it can be set for any patch. I also dont think its about vibrato, there is a kind of swell. IMHO.