In the second aliyah, Moshe tells the Jewish people that they are a unique nation and that G-d has dealt uniquely with them taking them from the midst of another nation with miracles and wonders. Also, the Jewish people heard G-d's voice out of heaven when they stood before Mount Sinai and received the Torah and knew that there is none other beside G-d. Moshe continues that we should always remember this and teach our children and children's children this same teaching. We should keep His laws and not stray after other gods.
This aliyah also contains a hint that the Jews will eventually be exiled from Israel because of their wrongdoing and be scattered among the nations as we are now. But Moshe goes on to say that we will eventually return to G-d, and if we seek G-d with all our heart and soul we will find G-d.