His wife, his love, Eurydice. His wife had been bitten by a snake and had died and went into the underworld.
He wanted to get his wife out of the underworld, and bring her back to the ordinary world, so he could see her again
Crossing the Threshold
Orpheus was very talented when it came to his music. He had made beautiful music with his lyre. All the people and animals of the land had loved to listen to his music. In the text on page 532 it states ". . .it was his lyre that heartened the men on those nights when they lost courage and despaired reaching their goal"
The Journey Home
The oridnary world is where Eurydice had got bitten by a snake on the day of her wedding. This is where Orpheus had played is music that was auspcious by all people and animals in the land.
Whe Orpheus had reached the entrance of the underworld ther ewas a three headed dog that had protected the entrance, but with his music he was able to get the dog to relax enough for him to pass through the gates.
After he had got his wife back from Hades, he was told no to look back at her until they are in the ordinary world. Stated in the tect on page 535 it states "Orphues's wish was granted . But ther was one condition : she must follow in his shadow and he must not pause, or speak or turn to look at her until they reavh the upper world." This shows the trust he must put into Hades to get his wife back.