il can function as a dummy pronoun, with impersonal verbs such as falloir (elsewhere translated as to be necessary), pleuvoir and other verbs related to the weather, sembler, etc. In other words, il is used to provide the clause with a subject but does not provide it with any additional meaning. (There are dissenting interpretations of dummy pronouns, but they are irrelevant here.) You can see a parallel to the use of the English it:
- It was necessary that he die.
- It seemed that she could not improve.
- It rained yesterday and will snow today.
If a construction that did not use impersonal verbs and dummy pronouns were desired, a phrase such as avoir besoin de (to need) could be used.
falloir can sometimes take an object pronoun, to, as you might imagine, indicate that something is necessary for the antecedent of the pronoun. Further discussion of that specific aspect is in the link provided in the comments.