They were continually devoting themselves to the apostles’ teaching and to fellowship, to the breaking of bread and to prayer. Acts 2:42, NASB
Most of the churches I attended in my life had something called “fellowship” and some even had space dedicated to it called “fellowship hall” or something similar. We had time after “church” that was called “fellowship time” that always seemed to be a relaxed time of visiting together and just being friendly with each other outside of normal “church stuff.” In the New Testament the word that is translated as “fellowship” as in Acts 2:42 (above) is κοινωνια or koinōnia, which Greek scholar Kenneth Wuest has defined as, “joint participation in a common interest or activity.” Instead of simply a friendly time of visiting together or a coming together for relaxation, κοινωνια, then, is a partnership, a sharing of something in common.