It is important to appreciate the scale of the comet's orbit compared to the Earth's orbit. The Earth goes round the Sun in a nearly circular path. The average distance is one Astronomical Unit (AU).
C/2020 F3 (Neowise) has an incredibly skinny elliptical orbit. It's closest approach to the Sun (perihelion) is at 0.3 AU, which is inside the orbit of Mercury. However, its furthest distance from the Sun (aphelion) is 500-700 AU.
By way of analogy, if Earth is like a boat that is sailing around a harbour, Neowise is like a ship that comes in from 600km out at sea, turns in the harbour and sails back out again.
As to whether we can see it or not, as @JamesK states, comets are usually visible for several months. It might be possible for a comet to approach, orbit the Sun and recede, entirely in the daytime sky. In that case, we would never see it. However, it is more likely that at least part of its orbit would be in our nighttime sky and so visible at some point. [n.b. by visible, I mean visible to astronomers with telescopes and image processing equipment - not necessarily to naked-eye amateurs].