When the block is intended for installation on a bench it is called a bench stone. Small, portable stones (commonly made of bonded abrasive) are called pocket stones. Being smaller, they are more portable than bench stones but present difficulty in maintaining a consistent angle and pressure when drawing the stone along larger blades. However, they still can form a good edge. Frequently, fine grained pocket stones are used for honing, especially "in the field". Despite being a homophone with wet in most dialects of modern English, whetstones do not need to be lubricated with oil or water, although it is very common to do so. Lubrication aids the cutting action and carries swarf away.
Now you may wonder, if a finer stone produces a better cutting edge why do I need a coarse stone at all? The answer is that finer stones work much more slowly than coarse ones. The amount of metal a fine stone removes with each pass is much less than what a coarse stone removes. If you have an edge with a good shape to it from a coarse stone, this is not a problem because the fine stone doesn’t have to remove much metal to improve the edge. If the edge is dull, it will take many times longer to reshape it with a fine stone than it would with a coarse one.