Who are the communion of saints in the Apostles Creed?

Epworth Methodist Church, Epworth, England

Every time we confess our faith using the words of the Apostles Creed, we say together:

We believe in the Holy Spirit,
the holy catholic church,
the communion of saints,
the forgiveness of sins,
the resurrection of the body,
and the life everlasting. 

Who is the "communion of saints" we speak of in this ancient Christian creed?

Read more at this link.