‘And all the gathered crowd kept silence; and they listened to Barnabas and Paul as they rehearsed what signs and wonders God had wrought among the Gentiles through them.'
Peter's words had moved them all to silence. Living in Jerusalem they had not really been faced with the heart of matters like this before. They must mostly have recognised the truth of what Peter had said, and that, of course, he was right, but they had not previously had to face up to its implications. They had gone on living as Jews because that is what they were. They had been brought up to it. And they would go on living like it. But they had not stopped to consider whether salvation was possible without it.
Then they continued to listen as Barnabas and Paul (in Jerusalem it was Barnabas who had the greater status, and probably spoke first) went through in detail what God had wrought through them, and the great signs and wonders that He had done. These signs and wonders would be seen as demonstrating His full approval. And they told them all that had happened among the Gentiles, and explained how many of them had responded to Christ and were now worshippers of the living God through Him, even in places where there was no synagogue. Then they explained how they now met in their own groups under elders and worshipped God continually, with the Holy Spirit active among them. They had formed ‘churches'. The full story of God's glorious activity was being explained so that all might know the facts for themselves.