This explanation of fellowship in the original language is really good....
Acts 2:42 Commentaries: They were continually devoting themselves to the apostles' teaching and to fellowship, to the breaking of bread and to prayer.
Barnes notes on the Bible
And fellowship - The word rendered "fellowship," κοινωνία koinōnia, is often rendered "communion." It properly denotes "having things in common, or participation, society, friendship." It may apply to anything which may be possessed in common, or in which all may partake. Thus, all Christians have the same hope of heaven; the same joys; the same hatred of sin; the same enemies to contend with. Thus, they have the same subjects of conversation, of feeling, and of prayer; or they have communion in these things. And thus the early Christians had their property in common. The word here may apply to either or to all of these things to their conversation, their prayers, their dangers, or their property; and means that they were united to the apostles, and participated with them in whatever befell them. It may be added that the effect of a revival of religion is to unite Christians more and more, and to bring those who were before separated to union and love. Christians feel that they are a band of brethren, and that, however much they were separated before they became Christians, now they have great and important interests in common; they are united in feelings, in interests, in dangers, in conflicts, in opinions, and in the hopes of a blessed immortality.
