The largest change and most obvious change that Finite Liquid brings to minecraft is the water - removing the source blocks, allowing it to flow more naturally in the area.
Oceans still contain an infinite amount of water, and are all still 'source' blocks, however using a bucket on an ocean block does not give you a source block but rather ten inches of water. While this does make filling up medium to large sized pools (or player made lakes) with buckets a time consuming task pipes and pumps have been included to aid with the transportation of water.
If you dump a bucket of water onto a flat surface, it will spread out inside a 5x5 square (covering ten blocks with an inch of water). Mining/digging a hole in the centre of this 5x5 square will usually cause the water to flow into it, however the occasional inch of water may be stuck on ground. The water will always try to flow to the lowest possible point, and if encountering a flat surface will always spread out. You cannot pick up water with a bucket unless there is enough water to fill the bucket (the same amount of water that you can pick up from a source block in the ocean). For the sake of ease of writing, we'll say the lowest amount of water a block can have is one inch, so every bucket can hold ten inches of water.