Basically, it's a grenade with a programmable time fuse. The soldier lases the cover that the target is hiding behind, the computer on the weapon displays the distance on a readout, the soldier pushes a couple of buttons to tell the munition at what distance to go off, the computer calculates the time and tells the grenade when to go off. The soldier pulls the trigger, the grenade launches and X number of seconds later the thing goes off. If you've done it right, it should burst just over the heads of the people hiding behind the wall.
However, there are *many* practical problems with this system as it currently stands. It's heavy, for starters. Can you figure out what the rest of them are?
I thought I read somewhere that those grenades are spin fused. The fuse counts the number of revolutions to judge distance down range. Of course now I can't find the article I was reading about it.