It's an allegory for God and Creation - book of Genesis stuff. Javier Bardem is God, who creates the world at the beginning. Mother, Jennifer Lawrence, quite the piece of ass in a sheer nightgown, is alternatively Mother Nature and the Mother of God (Holy Mary figure), or both. At the beginning, you see a woman crying in a burning house. Then God puts a crystal on a shelf and it revives the house to a point where Jennifer Lawrence is sleeping in bed and she wakes up, looking for her husband, God. She's working on their house the whole time, without help from God, trying to make it the way God likes it. She's always trying to figure it out, but God basically ignores her. He loves her, but ignores her. God is a poet who has writer's block and he can't seem to express his wants and desires and message at all. She's trying to help him, and she is upset that he can't seem to be inspired by her. The house they live in is in an idyllic wood, which evinces Eden, and Jennifer Lawrence says she wants to make it a Paradise.
Then comes Adam to the door, Ed Harris. Adam arrives as a lost and lonely guest who it is revealed is actually someone who heard about God and wanted to find him and meet him before he died. Weirdly, the Javier Bardem character happily invites him in and drinks with him, and hangs out, letting his wife go to bed, although the wife is concerned a stranger is in the house. She doesn't like the stranger, who resists being told not to smoke, and who brought a lighter into the house. While Lawrence is sleeping, he's smoking and drinking in the house while talking to God, and she wakes up and finds her husband in the bathroom with the Adam figure who is throwing up from drinking. She notices a wound on his back, and Javier Bardem covers it up and tells her to leave.
The next day, Eve shows up - Michelle Pfeiffer. Who is rude and immediately dislikes Jennifer Lawrence. She's like a temptress, always poking around and snooping. And,even after she is told not to go into Javier Bardem's study, she leads Adam in there and they accidentally break the crystal. The crystal represents love. Javier Bardem gets angry and tells them all to leave, but they come back.
Then the sons show up. First Abel, then Cain, and they're upset that the man, Adam, is being unfair in his will, and Cain ends up killing Abel. God puts the mark of Cain on him by bashing his head into the table. He's then sent off into the wilderness. Abel dies in the hospital, and then a bunch of Adam and Eve's family members come back to the house and are mourning. They are rude to Jennifer Lawrence, and they won't listen to her.
Suddenly, God gets inspiration, and publishes his poetry, and that's when shit hits the fan. People start showing up to meet god and they all think the writing is for them, but they all read it differently.
Eve ends up getting God to admit he wants a son and Jennifer Lawrence is upset, because God won't make love to her and she thought he didn't want a child. So, they get in a fight, God fucks her, and impregnates her. She ends up having the baby, but that's in the midst of the house getting crowded full of people who are not leaving them alone and who are fighting among themselves. Finally, the child is born and God wants to show the baby to the people. But, Jennifer Lawrence refuses. But, she falls asleep and wakes up to see that God had taken the baby. She runs out to see the baby getting passed among the crowd and she screams and cries to give the baby back and not to hurt the baby, etc.
It turns out, the people kill the baby, and you see the shredded corpse and people are eating his body and drinking his blood. Mother is pissed off at God and screams and yells, and God keep ssaying that the people are sorry, and they have to be forgiven for what they did.
Then Jennifer Lawrence goes nuts. She starts killing people and going crazy. And, the people go crazy fighting each other and trying to kill her. Kristen Wiig shows up as the Herald of God and she's shooting people in the head -- she's also God's publisher, by the way. And, just as she orders the people to finish off Jennifer Lawrence, she herself is killed.
Mother escapes the fighting and and house which is being destroyed and she goes down to the basement, releases a bunch of flammable liquid or oil, and uses Adam's lighter to burn it all down. All that's left is God and Mother, who is dying. He gets her to say that she still loves him, and gives him her heart, which is a crystal, which he digs out of her chest and she dies.
The house is burned down, and then you see God put the crystal on a shelf, and light comes out and a house is rebuilt, with a new woman in the bed who wakes up looking for her husband.
God gives one explanation towards the end for what he does - he creates "it's what I do."
Throughout the movie, Jennifer Lawrence keeps drinking a yellow powder sprinkled from an old looking medicine bottle, which helps her when she's feeling upset or sick. It's not clear to me what that represents. Maybe mother nature's way to heal herself to some degree.