system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why are nails or screws better in different applications and how do you know/work out which is best for what?
gpt
Nails have a little bit of give, while screws generally do not.  For this reason, nails are used when building with wood, as they can handle it when the wood flexes over time (due to weight, age, humidity, etc).

Screws provide a stronger, less flexible connection, which is preferred when things aren't supposed to flex.  Screws are used on decks specifically so that the boards don't loosen.  Screws are also easier to remove, so they are better for situations where the item will definitely have to be replaced.