The major arcana largely tells a story, where the fool goes through life growing, learning, and re-learning various lessons. All in all, however, the main attribute we find in the character is a blind innocence toward the path ahead. The Fool has never trod this path before, and has no idea what may befall them - for good or ill.
While other major arcana cards relate as much to where in the journey the querent may be, the Fool has no journey. The card itself is a symbol of a mindset, not a circumstance. When you've no idea whether you're coming or going; and when you've no idea what step is the right one to take/ This is the essence of the Fool.
The Fool as the Querent
The querent and the Fool are, in all points, interconnected. Why would they be seeking tarot if not for needing direction they can't find elsewhere? This is NOT a judgement of intellect! The fool is no dummy. And neither is the querent. Indeed, in all things a person can only know from where they've been. Just as the Fool is always implied as part of the journey of the major arcana (hence their number being 0), the Querent is always implied to be on any number of life journeys, learning lessons from the choices they make. Every step can be an opportunity to learn and grow, regardless of the outcome it brings.
If the Fool is dealt in relation to the querent, it signifies their place as not knowing the road ahead. This can be blind faith, or foolhardy progression. In either case, the first lesson is to trod lightly. And the second lesson is to seek direction before moving forward.
Past Card vs Outcome Card
When the Fool appears in the past, it signifies the lesson has only just begun. There is no mastery, and the first steps may even still need to be taken. The Fool signifies it's time to embrace the lesson and find your path. Nothing is holding the querent back outside of their own uncertainty.
When appearing in an outcome - or future - placement , the Fool is indicating the need to take risks. Most especially, there is the implication of a leap of faith here. (Though, if the reading includes reversed meanings, there may be a caution against making decisions blindly.) This decision signifies the beginning of some new journey for the querent - regardless of what their choice may be. And in their decision, there may be a number of outcomes already lined up like dominos ready to topple.
The Fool in Different Deck Themes
While most decks incorporate the imagery and meaning of the Fool along with the major arcana, it's important to account for the deck you're reading from and its tone and theme. Depending on the deck, the Fool may lean more toward a n aloof ideology, or a reckless state of inhibition. The difference lies between what story the deck tells of the whole major arcana, and what cards are dealt for the spread in question.