The question was asked on 01/01/2014, so this answer is very late it would seem. However, I only joined last week.
As for your question, I get asked that a lot. The reason why Paganism and Wicca have become synonymous is because of the New Age-fad borrowing bits and pieces from different traditions.
Paganism can be explained as such.
Wikipedia defines Paganism as "a broad group of indigenous and historical polytheistic religious traditions—primarily those of cultures known to the classical world. In a wider sense, paganism has also been understood to include any non-Abrahamic, folk, or ethnic religion. Modern ethnologists often avoid referring to non-classical and non-European, traditional and historical faiths as "pagan" in favour of less ambiguous labels such as polytheistic, shamanistic, pantheistic, and animistic." (https://en.wikipedia.org/wiki/Paganism)
You'll have to forgive me, as I don't have an etymological dictionary handy.
The above Wikipedia definition is fairly close to the mark.
The word Pagan/ism comes from the Latin word "paganus" which essentially means (If memory serves me right) "villager, rural dweller" etc. It has been used in derogatory fashion to label someone as being "from the back-waters, or wrong side of the tracks".
Moreover (and perhaps the reason why Christians refer to all who don't follow the three Abrahamic faiths as Pagans), an incompetent soldier in the Roman army would be called a "Paganus". Quite fitting actually, as most conscripts WERE from rural areas conquered by the Romans. (And of course, Christians refer to themselves as Soldiers of Christ/God....making all Pagans incompetent soldiers because we don't fight for their god).
So, the jargon aside and pre- (and miss)conceptions forgotten....
Paganism literally means, to be from a rural village, ie. to not be part of the organised establishment.
In New Age/Spiritual terms, Pagan/ism refers to anyone who is not Christian, Jewish or Muslim.
So, that brings us to Wicca, which actually falls under a sub-category of Paganism.
Think about comparing the words Pagan and Christian.
We all know a Christian to be a follower of the Christian faith. But, there are thousands of denominations and sub-cults in the Christian religion.
So too, a Pagan is someone who follows the "Natural Path" and a Pagan would fall into another sub-category, depending on which "denomination" he/she falls under.
Wicca is a form of Paganism. A Wiccan is a Pagan, but a Pagan is not necessarily a Wiccan.
There are many forms and types of Paganism. I myself follow my own path which overlaps with many traditions. Essentially, though, I am a Viking. That makes me a follower of the Pantheon of Norse Gods. I am actually somewhat rural too. So I am Pagan.
But, I am first and foremost He Who Is, then I am a Viking, then I am a Child of Odin and only then would I categorize myself as Pagan. (Having said that, I am a proud Pagan)
As for what Wicca is....
Hmmm...again, no reference books, as I had to get rid of my book collection.
But, off the top of my head.....
Modern Wicca made a resurgence in the 1970s/80s. What it boils down to is cosplay (costume play), acting and recital.
If you are interested in Paganism and want to go down the Wiccan path, I would suggest not joining a Modern Wiccan coven.
Either become a solitary practitioner or join a real Witchcraft Society.
Many new Wiccan (and other) groups pop up from time to time. Most who start these groups are as inexperienced as you, but crave the power that a position of authority (like a priestess) would grant them.
Real Witchcraft is nothing like the nonsense you see on television or read about in books. Those "grimoires" and "spell-books" are nothing more than a means to get rich off gullible people (this includes the "Positive Attraction" drivel).
A witch does not have to know any spells or recipes, although, it does help.
If you grow your own herbs, etc. and you make oils or ointments out of them, you'd be classed a White Witch (a Healer).
Many cultures call a witch (usually male, not female, but that's another topic all together :p ) by various names. Shaman, Elder, Crone, Hag, etc....
Some witches do cast spells. However, there is more to it than just speaking the spell and having willpower.
It really is a fascinating avenue of discovery. I myself dabbled in Witchcraft when I explored Alchemy. The two go hand-in-hand.
Ultimately, Paganism is not a choice, but a compelling.
Nobody can tell you what to believe, how to believe it or how to put it into practice.
The important thing about Paganism, is a simple "knowing" that you are following the path that is right for you (and those around you, as harmony is key).
Avoid egotistical people and "recruiters" with a silver tongue.
I'm sorry the answer is so long. I thought it best to be thorough.
I hope I answered your question.
If you would like more details, please feel free to ask.