One of the early writing prophets, Hosea used his own experience as a symbolic representation of God and Israel. The relationship between Hosea and Gomer parallels the relationship between God and Israel. Even though Gomer runs away from Hosea and sleeps with another man, he loves her anyway and forgives her. Likewise, even though the people of Israel worshipped false gods, God continued to love them and did not abandon his covenant with them.
The Book of Hosea was a severe warning to the northern kingdom against the growing idolatry being practiced there; the book was a dramatic call to repentance. Christians extend the analogy of Hosea to Christ and the church: Christ the husband, his church the bride. Christians see in this book a comparable call to the church not to forsake the Lord Jesus Christ. Christians also take the buying back of Gomer as the redemptive qualities of Jesus Christ's sacrifice on the cross.
–Wikipedia