Liz, is it a true hardwood floor or an engineered floor? Engineered wood floors move with changes in humidity and float above the subfloor so that this can happen. They are glued together and have a 1/4" wide gap between the floor and the wall for the movement to occur. They are normally finished on top of the floor at the factory.
True hardwood floors are solid pieces of wood (not plywood type material) and are not normally factory finished. These also move with changes in humidity but each piece is nailed to the subfloor. Small gaps between each board can occur during periods when the house is dry, like in the winter where you are heating it. These may have a gap between the floor and the wall but the gap will normally be very narrow.
Baseboards are made for covering the gaps and some situations may also require a piece of quarter round at the bottom of the base shoe molding. See you home center for available choices for these.