Click two items from the grid below and scroll down to see the description of how they interact together
The Afterbirth DLC not only added 120+ new items, but a whole host of new weapon synergies that have pretty darn cool effects. This page should help you figure out which ones you should be looking out for and which to avoid!
To see the effect of two items combined, click two items from the list above and they will appear on the pedestals above, along with their combined effect. To remove an item from a pedestal, click it. Simple!