Paul is bringing the gospel to the known regions of the world. He goes to Athens and sees shrines to every known god they could think of and just in case they missed one, they made a shrine “to an unknown god.”
Paul seized the opportunity and said he knew their missing/unknown god and he was Jesus Christ. It is the God who made the world and all that is in it. He doesn’t live in sanctuaries made by human hands and we as humans do not serve him because of our humanity but rather it is he who give everyone life and breath. He continued that our God does not need an image made from gold, silver, or stone. God just wants us to repent of our sins because we know that the price of our sins was paid for by the death and resurrection of Jesus Christ. That is what makes Christianity different.
Many people in Athens scoffed at the idea of the resurrection but some believed. For some it is hard to give up what they “think” they believe. But Paul sowed the seeds of the gospel and even though he continued on to Corinth people in Athens heard about Jesus.