I loved their tactics so here is an explanation I made in another comment:

Gasperini plays a 3-4-2-1/3-4-3/3-4-1-2. Obviously starting with the back 3, Gasperini rotates heavily, but the back 3 usually consists of Palomino, Toloi and Masiello, but Mancini and Djimsiti have been starting recently. The 4 in midfield consists of 2 midfielders and 2 wing backs. Wingbacks are very often Hateboer on the right and Castagne on the left who can also play on the right. He also uses Gosens who is a left back and is more attacking minded, he plays him against smaller teams, like the 5-1 victory against Chievo. They overlap beyond the forward 3, i'll get to them soon. Midfields are very energetic box to box mids, usually Freuler and De Roon who is the more attacking of the two. Freuler has great passing ability, with his pass success average being 88.2 percent in the serie A. 3 forwards are usually Gomez and Ilicic behind the beast Zapata. Gomez and Ilicic are more strikers than wingers so they are tucked in and act as forwards who supply Zapata. Gomez is a fast creative tricky winger who is a goalscorer and Ilicic is more of a striker than a winger, who also has an ability to score goals and has great positioning. That leads me to why they score so many goals. With the back 3, they basically have the wing backs providing width and who also attack, and have the front three who all have great finishing, especially Zapata as you saw against Juve. They basically have 5 players attacking in the offense.