It's not Easter, nor is it Passover, but it takes place during Passover week, as did his death. It's a celebration of Jesus' death, resurrection and return to heaven... which makes it more like Easter. However, the resurrection is not one of the body, but as an immortal spirit who stuck around earth to talk to some people for a while before joining his father in heaven.

My Mom was a JW, and I attended all the meetings and bible studies as a kid. When I was little, I always thought we were celebrating Passover like the Jewish kids at school, but the unleavened bread and wine was a remembrance of the Last Supper, not Passover, so that makes it a little like Communion, except not everybody eats and drinks, only the elders of the congregation.

The whole not-celebrating-holidays thing is because they reject those holidays -- namely almost all of them -- which have their ultimate roots in pagan culture, or those that are nationalistic, which is viewed as revering a country more than God.