The tall coconut trees are the most common ones. Not sure whether the yellow fruit of the dwarf varieties is edible.
The green coconuts are the young ones. The water is sweet, and the flesh is translucent and soft. So these are for drinking.
If they are not plucked, they eventually ripen and turn brown, before dropping. You can use them whether you pluck them from the tree or after they have dropped from the tree.
The brown coconuts are called "old" coconuts. They are usually dehusked, and the flesh (which is thick and hard and rich with milk) is grated and squeezed to make coconut milk, which is used for cooking. The water is usually discarded, since it is sometimes semi-fermented (which is why it is occasionally fizzy, or "carbonated" as you call it). There is also usually a fairly large embryo inside the coconut (called the "heart") which is sometimes eaten. Has a nice buttery, nutty taste.
In case you're wondering, I grew up in a house with lots of trees, including coconut trees, which I used to climb. So I am talking from first hand experience.