Suppose you have some business logic that subtracts the cost of a transaction from an account balance and returns a new account balance. These things are probably integers, but in many languages you don't have to specify that. You write this function, then later your coworker comes across it and passes it a double. You might end up with weird small discrepancies in account balances (or mysterious errors that only happen sometimes) that could be totally prevented at the time your colleague wrote the code via static analysis, if you use put some logic (costs and balances are integers) into the types.

This can be more sophisticated, like "this function requires a sorted list" so lets make a sorted list type, or packaging things up into biz logic types (a cost type that contains an integer instead of just using integers), but you can catch a wide variety of errors with static analysis if you make your code and logic amenable.