Well, imo, all Wiccans are Pagans, but not all Pagans are Wiccans,
if that  makes any sense. 

I can understand that, but how are they related? ;)

I think Kim might have addressed this, but I'll do so too (it's a hobby
of mine, you know).

All Pagan religions believe in several common tenets:

A belief in multiple Gods or Spirits (God and Goddess, Gods and Goddesses,
animistic spirits, totems, etc.)  that are expressed through nature. Judeo/
Christian religions see God as apart from the earth (God created the earth  
from on high, in Heaven). Pagans believe that the earth and all who live 
thereon are expressions of the deities, be they Gods, spirits, or whatever.
Christians see time as a line--the earth was created on a particular day, and
will end on a particular day. All Pagan religions see time as a series of
cyclic events---the seasons, the phases of sun and moon, the phases of a 
persons' life, etc. 

All Pagan religios share a belief in the continuence of the soul within 
these cycles---karma, reincarnation, the Summerlands of rebirth, etc. 
(As opposed to the christian concept of the destination of the soul---Heaven
or Hell). 

Wicca is specifically the European Pagan religions, as interpreted by several
teachers and authors within the last century (though some of us practice the
religion, or aspects of the religion, that predate these teachers, and have
been preserved in one form or another through the Burning times). There is 
not now, nor has ever been, a unified Wiccan religion---each community and 
tribe/clan in old Europe had its own practices and myths, usually based on
common elements. But in modern Wicca there are cohesive traditions (I use
the word "Tradition" to denote a system of worship that has been handed from
teacher to student for at least three Craft generations---about 15 years). 
Two  of these come from the earliest modern Wiccan pioneers---Gerald Gardner
(Gardnerian tradition) and Alex Sanders (Alexandrian tradition). 

All Wiccan traditions center upon the worship, through ritual, of a God and
Goddess, or a pantheon of Gods and Goddesses, generally European or Egyptian
in Mythic origin. Most Wiccan traditions reverence the teachings of two 
liturgical pieces, the Wiccan Rede (see a prior post) and the Charge Of
The Goddess. Most Wiccan traditions center upon a relationship between
a Priestess and/or Priest and their students, culminating in an initiatory
experience that ordains the new initiate as a Priest/ess, and involves vows
to serve the Gods of the tradition or coven. 

In the last decade, many people new to Wicca have sought to use the Wiccan 
ritual model as a basis for ecclectic blends of other Pagan and non-Pagan
traditions, creating a synthesis that varies from individual to individual
and from coven to coven. This synthesis, called Ecclectic Wicca, often 
lacks some of the bases of older, more established traditions, sometimes
through lack of training in these, other times because the teacher or
seeker does not deem these appropriate to her/his work.