The church is sometimes called a fellowship; it is a network of relationships. We all need to give and to receive fellowship. We all need to give and receive love. Fellowship means a lot more than talking to each other about sports, gossip and news. It means sharing lives, sharing emotions, bearing one another’s burdens, encouraging one another and helping those who have need.
God made us social creatures. We want to interact with other people. If a person's social life does not center around the church, he will be tempted to socialize in places with not nearly as positive an atmosphere as the church. The church gives the members plenty of opportunities to fellowship with one another. True fellowship always includes the Father and the Son of God. If the presence of God is not real in the fellowship, it will be nothing more than a social club.
The First Church did not need to emphasize fellowship — they formed them naturally. The reason we find it necessary to emphasize them today is that society has changed so much. To form the interpersonal connections that ought to be part of Christian churches, we need to go out of our way to establish Christian friendship/study/prayer circles.