Applying a bucket of water to an empty block (with or without a back wall) will empty the bucket and create a block of water at that position. Once placed, the water will behave according to its surroundings, typically flowing to the lowest empty point confined by solid blocks. This is the easiest process for transporting non-ice water to a new location.
Filling and emptying a bucket of water in a confined space is part of one method to generate water.
If a bucket of water is emptied onto an uncontrolled fire, the fire will be put out.
If a bucket of water is emptied onto ice, the water will likely freeze immediately into another block of ice.
If a bucket of water is emptied in space, it will immediately freeze into ice, allowing structures to be built there without having to build up first.