A very powerful soul might the energy to have direct contact with ours. If we have had direct contact with God on earth, it will continue afterwards. That will be heaven. If we have no contact with God or anyone else, it will be hell. You might say that purgatory is a state of being in which our contact with God is not strong, but still exists.
Purgatory is like a second chance.
We can help a person in Purgatory reach heaven, by our communication with God. We act as go-betweens helping to bridge the gap between them and God. The word for this communication is Prayer. We pray for their souls and they get to heaven.