I guess you mean in "Hotspot *hat"? The asterisk there just means that it's a pointer. All of the following are the same:
[code]Hotspot *hat = Hotspot.GetAtScreenXY(mouse.x, mouse.y);[/code]
[code]Hotspot* hat = Hotspot.GetAtScreenXY(mouse.x, mouse.y);[/code]
[code]Hotspot*hat = Hotspot.GetAtScreenXY(mouse.x, mouse.y);[/code]
[code]Hotspot * hat = Hotspot.GetAtScreenXY(mouse.x, mouse.y);[/code]
No matter where you put the space(s), the asterisk is, as I said, because it's a pointer. If you're not familiar with pointers in AGS, you can read up on them in the manual, and
this tutorial I wrote might also help.

The basic idea is that you're just reusing an existing Hotspot instead of creating a new one (which you can't do from the script anyway, so you have to reuse them).
Edit: Oh, and if you're wondering, I named the pointer "hat" to mean
Hotspot
AT the given coordinates. You can name it whatever you like of course (whatever makes the most sense to you!!), but this is just the type of name I use when checking what Hotspot the mouse is over.