"The Art of breaking blocks", "To break a block, click and hold your left mouse button on a certain block. Depending on the block, it can take from a 10th of a second, to multiple minutes. 
Of course, you don't want to break stone with your bare hands. You need tools to efficiently break blocks. 
Pickaxes break stone and ores. 
Axes break wood and trees.
Shovels break dirt and sand.
Swords are decent against everything, but won't drop any blocks from resistant block types.
Some block types are so resistant that you can't harvest them by hand, at all. You'll need the correct tool to do that. Stone, for example, needs any pickaxe to be broken. To break iron ore, though, the wooden pickaxe won't help you anymore - you'll need stone pickaxes then."
