First the writer of Acts briefly characterizes Stephen's activity. "Full of faith" means, more properly, full of grace, χάριτος, that is, of the Holy Spirit (cf. Acts 4:33), or generally of the gifts of the Holy Spirit.
This expression indicates the abundance and variety of the spiritual gifts active in Stephen. "And power" means wonder-working power, as is clear from the subsequent indication of the signs and wonders performed by him among the people.
This indication of Stephen's miracles is noteworthy. Until now signs and wonders had been performed only by the Apostles. From this time, the gift of miracles is communicated by the Holy Spirit also to other believers for the good of Christ's Church, spreading ever more widely in the world.
"He performed great wonders and signs among the people." Serving in his new office especially among the poor, widows, and infirm, Stephen could have had many occasions to benefit the people by miraculous healing of illnesses and infirmities.
He also benefited them by spiritual consolation, encouragement, strengthening, help, prayer, and the like. Thus, as everything shows, Stephen's name enjoyed special respect and love among the people.