And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it. - Matt 16:18 KJV
For the husband is the head of the wife, even as Christ is the head of the church: and he is the saviour of the body.
For no one ever hates his own body, but he nourishes and tenderly cares for it, just as Christ does for the church, For no man ever yet hated his own flesh; but nourisheth and cherisheth it, even as the Lord the church:- Eph 5:23,29 KJV
When I was a child, I thought church was a place you went on Sunday, because that's where people were supposed to go. It was the right thing to do, part of the proper way to be a person. I was shocked out of this way of thinking by my church's deafening silence after my father died. But its residue led me after 20 years to join another church, until a conflict among its members drew me in. After it was over, I became a wanderer, visiting many churches, joining none, and not going every Sunday. While I was still a regular churchgoer ("churched," they call it) I became a Stephen Minister. As an extension of my ministry I even started a cyberchurch, the Virtual Church of the Blind Chihuahua, of which this blog is a part. So again, what is Church? Am I still a part of it, and is cyberchurch really church?
Objectively, Church is the social network of all the believers, the clergy, and God (who, according to Church doctrine makes Himself available to the Church as a person - any and all of three persons to be exact). In the medieval Catholic way of thinking, the Church as social network formed an acyclic graph. Each person is represented as a node (like a Tinker Toy connector for you old folks), and each link represents an association or connection from one person to another (like a Tinker Toy stick). The graph starts with God, with links going from God to the Pope, from the Pope to the Cardinals, from the Cardinals to their Bishops, from the Bishops to their Priests, and finally from the Priests to the congregations of their People. The Protestant innovation was to make the network cyclic by positing a direct connection between every node (person) and the network hub (God). From a Social Network/Graph Theoretic perspective, the old Wars of Religion between Catholics and Protestants in Europe were over a change in topology.
Being a Protestant, I believe not so much that I keep up my connection to God through prayer, but that God keeps up God's connection to me, without my deserving the favor. This implies that I am still connected to the Church social network through its hub, through God. But there is more to Church than that.
Church has always meant communal worship. Not online, not in front of your TV, but in the physical presence of one another, the entire community of the faithful gathered together. A huge part of the love that Jesus commanded us to have for one another is attachment, a term which refers to the way mammals in close proximity influence each others' metabolic and neural (especially limbic system) rhythms. This occurs through postural cues (body language), gesture (including touch), and lots of other ways, including even the sound of each other breathing. This communal limbic resonance and limbic regulation is probably responsible for the statistic that regular churchgoers are healthier and live longer than the unchurched.
Perhaps the staid nature of worship in the mainline liberal Protestant denominations explains their decline in membership. We mammals crave limbic togetherness, which is mediated by our rhythms. Would it really diminish our neocortical liberalism if we had a little shoutin' and foot stompin' in the pews? But how much more would it revive the church if we took on the task of actually caring for one another?
Church is not only in your rational neocortex, but also in your emotional, soulful limbic body-mind - not only in your head, but in your heart. Cyberchurch cannot replace physical congregation. The Virtual Church of the Blind Chihuahua is merely an add-on, a sop to those of us who live too much in our heads, and a source of provocative ideas for those of us who don't.
Of course, there is infinitely more to Church than I have mentioned here. I have not even touched on the spiritual dimension, what it means to be a servant of God in community with other servants, the vulnerability of Church to the shadow-side of human organizations, etc. I've written about some of that elsewhere. For the rest, you might try asking your pastor.
 For more on social networks see Albert-Laslo Barabasi, Linked.
 For more on attachment, limbic resonance, and limbic regulation see Thomas Lewis, Fari Amini and Richard Lannon, A General Theory of Love.