This week's story is a wierd one but it's quite important. In between this week and last week, Lot was captured by some evil kings, and Abram helped some other kings defeat the evil kings. This week started with Abram refusing to take any riches from the good kings. He said that he trusts God to give him good things.
Abram showed great faith here, but as he came back to his dry, empty land, it felt hard to trust God. God came in and asked Abram to look at the stars and count them. Abram couldn't. God promised that Abram's decendants would be like the stars, too numerous to count. Abram had a hard time beleiving this, because he and his wife were too old to have kids.
God instructed Abram to cut a cow, a goat, a ram, a turtledove and a pidgeon in half. This was how people in those days made a deal; both parties would walk between the two halves, saying they would both hold up their ends of the bargain. However, in this case, God had Abram go to sleep and then God walked through the animals by Himself. This showed Abram that God was the only one who had to do something, and Abram just had to trust God.
The same is true for us today. God has promised to live the Christian life through us. We can't do it by ourselves. When we try, it always goes wrong. We need to rely on God to do it and He will. He perfectly lives through us. We can rest in His activity through us.