In Reformed theology there are various ways to describe Christ’s church. One of the descriptions is to distinguish between the church militant and the church triumphant. This is not to say there are two churches. It is simply a way to explain the state or degree of Christ’s church. Christ’s church exists in a twofold state: on earth, and in heaven. Some of his people have died and gone to be with him; others of us are still battling sin and evil here on earth. The church in heaven is at rest, the church on earth is in a struggle. Again, this is not to divide Christ’s church, it is just a way of explaining Christ’s one church here (on earth) and the church there (in heaven). Francis Turretin’s comments on this topic are excellent (I’ve edited them for ease of reading):
Here we walk by faith, not by sight;
while there, faith being changed into sight, place will be given for sight alone.
Here hope sustains;
there fruition will satisfy us.
Here the word and sacrament are the mirrors in which God presents himself for contemplation and the means by which he draws near to us;
there we will behold God face to face without a veil or means and intimately enjoy him.
Here is the place of groans and sighs, of the cross and trials because we live in a vale of tears where we are continually attacked by enemies and pressed by innumerable evils;
there, however, is the place of joys and exultation because, being delivered from all evils, there will be nothing which can bring weariness or grief to us, nothing, on the other hand, which will not contribute to our solid and constant gladness.
Here will always be the place for prayers and wishes to avert the evils which threaten us and procure the blessings which are wanting;
but there in the absence of all evil and the presence of all good, there will be nothing anymore for us to fear, overcome or desire. There will be no need to weary God with prayers, the witnesses of our need, but praises giving glory to him for his manifold wisdom, invincible power, perfect justice, inexhaustible goodness and unspeakable mercy, and other wonderful attributes in which the works of nature and grace, in the world and in the church, in creation and in redemption, in the gathering, protecting, sanctifying and full glorification of his church he has exercised and will forever exercise.