As the situation, the Fool could represent a departure from from pretty much everything previously known, leaving the comfort zone, striking out into the unknown without thought or regard to consequenses... it is embarking on some new journey, following a dream, an impulse.
Possibly foolish, filled with optimism and lack of fear but mainly ignorant, due to lack of experience, lack of knowledge, lack of baggage.
So the Fool as a situation could be trying something new and unknown, not letting the fact that you know nothing about it or have no expertise in stop you from trying... it could be anything from trying out a new recipe in a cookbook, deciding to enroll in classes or selling off your stuff and moving across town or across the country, backpacking across Europe...