Oooooh, where to start...
I don't know where to start. [Edit: I eventually found where to start, after much toing and froing! lol]
A few decades ago it would have depended on which Druid group you asked, now it's even more complicated as it depends on which individual Druid you ask.
OBOD, being organised more in the style of a mystery school, leaves individual beliefs up to the individual. There are Pagans, Christians, Atheists and Buddhists, at the very least!
Also how does Druidry differ to Shinto, and Heathenry?
Some succesfully combine Druidry with these. Especially with OBOD. Although OBOD differs in that it doesn't seek to reconstruct ancient belief and has an initiatory structure based on the Western Mystery Tradition.
Other that attempt to reconstruct Druidry or Celtic religion as a native tradition of the British Ilses and/or Western Europe will differ in respect that these traditions represent geographically distinct traditions.
Can someone explain to me the rankign and organizations within in Druidry too please?
In OBOD there are roles, but not ranks as such. Each grade represents a person's progress through the OBOD course, not how important they are or their function in the Order. There is no priesthood or clergy here. There are roles like the Chosen Chief, Pendragon, Scribe and Modron, but they are more symbolic and spriritual roles of guardianship in the Order than figures of authority.
Main Druid groups I can think are:
TDN- The Druid Network
OBOD- Order of Bards, Ovates and Druids
ADF- Ár nDraíocht Féin
AODA- Ancient Order of Druids in America
BDO- British Druid Order
RDNA- Reformed Druids of North America
Each with a slightly or radically different take on Druidry. And there's plenty more, many are offshoots from these ones.
Here's an interesting article outlining the difference between OBOD and ADF:
http://www.adf.org/about/basics/adf-and-obod.htmlI've yet to read it thoroughly but it might give you an idea of the differences between many modern Druids and Druid groups. It's actually written by the Grand ArchDruid of AODA, John Michael Greer.