what are the differences between paganism and druidism ??

i understand quite a lot about paganism, but how is it different from what the druid followers believe ??
but why do people call themselves druid ??if they are pagan OK, but what exactly do they do and believe ?/

Druidism is a specific type of paganism (just like Wicca is a specific type of paganism).

ADD: Though there are many people who simply call themselves Pagans, it is still just a general term for many different open theistic beliefs that are only loosely associated.

druidism is a form of paganism

yup. me too. paganism is an umbrella term that's used to describe the natural spiritualist traditions of native peoples all over the world. before THEY came and forced us all to be like THEM or suffer and die.

Druidism IS Pagan.

I think druids followed along with hierarchical leadership, like the major churches of their time. All pagans and some druids are polytheistic though, the way I understand it. Not all druids are polytheistic....again ....to my understanding..

Paganism is an umbrella term that includes many religions. Some examples of Pagan religions are Wicca, Druidity, Setian, Shamanism, Asatru, and others.

ORGINIZATIONS:
There are a few Druid organizations. The two I am most familiar with are the Order of Bards, Ovates and Druids ( http://druidry.org/ ), and Ar Utrecht Fein ( http://adf.org ). Other organizations exist like The British Druid Order ( http://www.britishdruidorder.co.uk/ ).

BELIEFS AND PRACTICES:
Druidity is mainly an offertory-centered religion of worshiping the Gods, ancestors, and nature spirits. ADF is one of the only Druid organizations that is Pan-Celtic/European in the Gods we hon our. Most Druid organizations only worship Deities from the Irish Pantheon. Modern Druidry is built largely around writings produced in the 18Th century and later, plus the relatively sparse Roman and early medieval sources. Though places like Stonehenge and similar Stone Circles were built long before the original Druids came along, similar places are used and built by Druids today.

Main differences between Wiccan and Druidity:
In Wicca, sacred space is made by marking off a closed circle and calling guardians/watchtowers and so forth. Wiccan sacred space is closed off and people are not free to move in and out of the space until the rite is ended.
In Druidism, sacred space starts with a central location, the altar, and extends outward. A circle or any other means do not close off this space. Druids are free to move in and out of the space, but being respectful should be something one should consider.
In Wicca, making sacred space and other forms of ritual preparation take a while to finish and go through. I have also noticed that many wiccans will say the "work with" their Gods, giving me the impression that worship is not a key focus.
In Druidity, the ritual preparation takes way less time. More focus is spent on offerings, sacrifices, and things to honour and commune with the Gods.
In Wicca, magic seems to be a big focus. The magic from Wicca stems mainly from The Golden Dawn, as evident in the circle, quarters, and general spell setup. The focus of this type of magic is in the persons focus, energy raised, and symbols used to aid the goal. The aid of a Deity may or may not be requested.
In Druidism, magic is looked at a bit different. The focus is not so much on the mechanics of symbols and things, but rather on the Gods and asking for their aid. Energy is often still raised and directed though. Druidic Ritual is more about strengthening our relationship with the Gods, Ancestors and Spirits of Nature. Magical workings are of secondary importance.