What does the Communion of Saints mean?

The Catechism of the Catholic Church teaches:

"The intercession of the saints. "Being more closely united to Christ, those who dwell in heaven fix the whole Church more firmly in holiness. . . . They do not cease to intercede with the Father for us, as they proffer the merits which they acquired on earth through the one mediator between God and men, Christ Jesus . . . . So by their fraternal concern is our weakness greatly helped."⁴⁹⁵

Do not weep, for I shall be more useful to you after my death and I shall help you then more effectively than during my life.⁴⁹⁶I want to spend my heaven in doing good on earth.^{497"  (Catechism of the Catholic Church #956)}

The Church is one, holy, catholic and apostolic. The one Church is in constant fellowship with the Church triumphant, Church militant and Church suffering.