This mod allows you to build and mine things really quickly.
You can do this by tapping two blocks. After that all the blocks in the area between those two blocks will be mined or placed. The two blocks you tap determine what the area will be filled with (for example, if you tap two dirt blocks, it'll be filled with dirt). With mining and building in survival it'll drop the blocks and take blocks from your inventory, in creative it won't drop/take blocks.
These items are quite expensive to get in survival though, because they are pretty OP. They each cost a diamond block and the Mining Wand also costs 2 extra diamonds.