Quakers do not share a fixed set of beliefs. Our unity is based on shared understanding and a shared practice of worship, not on our beliefs all being the same. There is no need to be in unity with Quakers on every issue in order to be part of our meetings.
There is a great diversity within the Quakers on conceptions of God, and we use different kinds of language to describe religious experience. Some Quakers have a conception of God which is similar to that of orthodox Christians, and would use similar language. Others are happy to use God-centered language, but would conceive of God in very different terms to the traditional Christian trinity. Some describe themselves as agnostics, or humanists, or non-theists and describe their experiences in ways that avoid the use of the word God entirely. Quaker faith is built on experience and Quakers would generally hold that it is the spiritual experience which is central to Quaker worship, and not the use of a particular form of words (whether that be “God” or anything else).
Not all our beliefs are so diverse. Some of our spiritual insights, which we call our testimonies, spring from deep experience and have been reaffirmed by successive generations of Quakers. These testimonies are to simplicity, peace, integrity, community, equality and stewardship. You can find out more about these testimonies, and how we live them out in our day-to-day lives. We suggest exploring the Faith and Practice of the Southeastern Yearly Meeting.
There are many explanations of Quakerism in publications and on the web.