Introduction
She is a First Class Goddess (Type 2) that works for Heaven, granting wishes for humans.
They only grants wishes for good humans and that's were the protagonist, Keeichi comes.
Keeichi is a 22 old student that studies in Nekomi's Technology Insttute, he was born under an unlucky star and due to bad luck falling upon his daily life, he was granted a single wish that he used to: "I wish for a goddess like you to stay by my side forever" and that's how Belldandy's life at athe human world starts.
Personality and Prowess
Belldandy is depicted as a caring, calmand kind goddess that tries to help those around here. (like Vina help her shinki

), the more she meets Keeichi friends, colleagues and other people around them, she helps, including her sisters who eventually come to live with her.
Despite having a kind nature, Belldandy have showed signs of jealously at times when other girls looked like they were in love with Keiichi. Also, she has great powers and will fight if necessary to defend her family.
Although something more implicit, Belldandy also seems to have some sort or natural luck aura such as those around her have luck (as showing in epi 2-3 when Keiichi plays mahjong and wins every time).
As for her personality, the goddess was initially more naive and unknowing of human world, she was marvelled to learn new things about that world as well as helping people who met her along the way.
Relationship with Keeichi
At the start, Belldandy only was in human world because Heaven's rules only alllowed her to stay close to Keiichi, but as time goes, she gradually develops feelings for him (as he does). Although the story is a romantic comedy with more slice of life than battles, it also talks about the "everyday" battles like those of Keiichi who needs to work, deal with unluck and still has troubles with demons since his Goddess started living with him. Belldandy as a companion helps Keiichi during those days they live together and affects positively his life.
I was a 3rd party, not a townie or mafia.