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They have different dieties?

Was your question more about how they run their perspective faiths & practices, their politics? I can't really explain that to you in detail, I'm not of them.
Wiccans tipically do not allow children under the age of 18 to become members of their covens, unless the student has parental consent & ussualy not even then. This is done mainly for legal reasons, there are initiation practices that many Wiccans hold to, that if a child were to get involved would border on the *****. They also want to ensure that members of their faith, when initiated can be resposible with themselves & the faith, & not fall into fluffybunny land.
Some Pagans I have seen do allow children, though it depends on which type of Pagan faith they happen to be practicing. The problem with trying to explain how Pagans run their faith, theres not just one Pagan faith, theres a multitude. Not all Pagan faiths have the followers practicing witchcraft or other types of magic or directing their politics, some have only the Gods or demons possesing such powers, others have just a single member of their group having knowledge of such things with perhaps an aprentice.
They do have different God(s) from faith to faith, laws in each faith may be defferent depending on the personality of these entities.

"Paganism" is an umbrella term. That means that it's a word that covers a wide variety of things: it's ambiguous. A pagan religion is any religion that fulfills these two requirements:

1. There exist more than one god
2. There is reverence for nature (worshiping Mother Earth, in a way)

If any religion meets these two requirements, it is a Pagan religion. Wicca is one such religion, one of many. I'll direct you to wikipedia.org, and search "wicca". That should give you a good start into what Wicca is.

There are several definitions for each, so I'll give you a more thorough rundown of the perspectives; Axeman did a good job bringing up some of them.

Paganism
This term used by the general public to refer to any religion that is not Abrahamic in origin.

It has also been used historically (not as much today) to describe those without a faith.

It is used as a synonym for Neopaganism by both Neopagans and others describing the modern Pagan movement.

Probably the best definition to use for Paganism is similar to what Axeman said. A Pagan religion is any religious system whose conception of deity includes (but is not limited to) polytheism, pantheism, and animism. Additionally, deity is usually viewed as immanent (manifest within nature) and personal. There are often transcendent aspects which are monotheistic in nature but are impersonal in nature (Example: The Brahman in Hinduism). Finally, since the immanent, personal deities usually are metaphors for natural forces, Paganism can be said to be Nature-based (Example: Ra representing the Sun in Egypt).

NEOpaganism is a modern recreation or revival of old Pagan systems which have fallen out of practice (Example: an individual worshiping the Greek Gods is always a Neopagan). It may also refer to individuals practising an existing Pagan religion who have no direct cultural ties from which to claim that religion (Example: an American practising Shinto who has no Japanese heritage or direct ties to Japanese culture would be practising "Neo-Shinto").

Wicca
There is some debate in terms of what does and does not constitute Wicca, but Wikipedia generally does a good job of presenting that. Additionally, THIS website provides a good summary of the key points.

pagan was a derogatory remark used by christians to refer to non-christians.