From First Corinthians by George T. Montague, SM, commenting on 12:4-6:
Here Paul describes these “spirituals” (pneumatika; 12:1) by three other terms: they are “charisms” (charismata, translated here as spiritual gifts), different forms of service, and different workings. A fourth term is used in verse 7, “manifestation of the Spirit.” Each depicts a different aspect of one and the same phenomenon. On the one hand, they are gifts, not something one produces by one’s own efforts, and hence we should be careful not to equate them with acquired skills, although the gift could bring a new and Spirit-filled anointing to such abilities. A musical ability could, for example, become a gift of the Spirit to the degree that it is placed lovingly at the service of the community, so that it is no longer entertainment but a ministry that truly builds up the body and is recognized as such (see 14:26).
That the gifts are different forms of service indicates that they are not given primarily for the benefit of the individual, though if a gift is a work of the Spirit, there would normally be a good effect in the one exercising the gift, as Paul will later say about praying in tongues (14:4). Nor are they given to establish a spiritual ranking or elitism. Rather, they are given for the good of the community and should be governed by that purpose. Different workings refers to activities that take place in the community and that are inspired by God.