I am actually quite surprised I didn't see many fourums discussing this topic, but anyway here goes.
The summerlands are, in traditional Wicca, a place where a spirit goes after it's physical body dies. It is, in a way, the middle ground between one life and the next. They are viewed both as a paradise, and a place to reflect on the past life, and decide what you have learned from that one before moving on to your next. Some Witches with less traditional views see at as more like the Christian heaven, an eternal paradise where they can experience the divine personally and meet their deceased family and friends. Everyone sees the summerlands differently, both in belief, and when they experience it after death.
Any questions,mail me.