The chapter
Simply Abram says he is still childless and that a servant will inherit. He is taken outside and told to count the stars. He believes. Then he asks for proof, and a covenant is cut in the dark.
Context Verse 6 is one of the most quoted sentences in the Bible and it is quoted in this app already: Romans 4 is built on it, and a reader can open that chapter and see what Paul does with it. Note also that belief at verse 6 does not stop Abram asking for proof at verse 8, and the text does not treat the question as a failure.
Verses 7-21
Simply Animals are divided and laid opposite each other. Abram drives off the birds of prey, then falls into a deep sleep and a great darkness. He is told his descendants will be strangers in another land for four hundred years and will come out. Then a smoking furnace and a flaming torch pass between the pieces.
Context Only one party passes between the pieces, which the reader can see in verse 17: Abram is asleep. The reason given for the delay at verse 16 is not about Abram's descendants at all but about the people already living there, whose iniquity is said not yet to be full, and the text offers it as a reason without expanding it.