What is fascia? The fascia is the long, straight 'board' that runs along the eaves of the roof & the edges of the rakes. They are attached directly to the roof trusses, at the eaves.
They support the gutters & drain pipes. and functions as trim giving the edges of a roof a clean and even appearance.
Fascia boards are very noticeable, so most home owners paint them or install vinyl or painted metal fascia boards to blend in with the color palette of the rest of the house.
The images are clear examples of how much they enhance the 'finish'look of a roof.
What is soffit? The soffit closes the gap between the wall of the house and the fascia. Soffits with vent louvres or holes are installed under the eaves of roofs. Closed soffits are installed under the rakes of a roof. They are the air intake part of a roof's ventilation system.
Most soffits, in use today, are fabricated from vinyl or aluminum. Both materials are impervious to the forces of weather. That is especially important considering that soffits can be easily exposed to water, such as, over flow from unkept gutters, ice dams and extreme wet weather conditions.