Infinity focus on prime lenses?

I'm looking to purchase the Nikon AF-S 50mm f/1.8 G. If it is a prime lens (focal point stays at 50mm), then why is it capable of focusing to infinity? I'm a bit confused on that part. If someone can clarify this, it would be extremely helpful!

You're messing up focal length with focusing distance.

The focal length relates to the angle of view that the lens produces. The shorter the focal length, the wider the angle of view ("zoomed out"). The longer the focal length, the narrower the angle of view ("zoomed in")

The focusing distance is the distance at which objects appear sharp. Objects of a different distance will be blurred. A lens with a focusing distance that is fixed at 50mm would be pretty much useless, as it would only be able to take sharp photos of objects that are 50mm away from it. Not more, not less.
But fortunately focal length and focusing distance are different things, so we can have lenses that focus at different distances at different focal lengths (angles of views).

Many lenses can be focused * beyond * infinity - mainly for infrared film.

You're a little confused. 50mm is the focal length which, unlike your 18-55mm zoom lens, is a fixed focal length - no zoom.

The AF-S 50mm f1.8G can focus from 1.48' (slightly less than 1'-6'') to infinity.

A lens that only focused at 50mm would be all but useless.

The measurement of focal length is from the focal plane (where the sensor or film is), to the focal center of the lens.

The focusing of the lens occurs outside of this spot, usually by one or more lens elements that move in and out, either in front of, behind, or both.

So the focal center of the lens never changes, regardless of the focusing action.

Normally i wouldn't respond to this but the others just loaded a pile of misunderstanding on you.

50mm means that is the distance from the front lens element to the focal plane when it is focused at infinity. This is just a rating of the lens, it does not mean the lens is always 50mm from the focal plane. Most nerds on here have never used a primary lens, just zoom lenses with internal focus so they don't understand how either works. When a primary lens focuses at a subject that is closer than infinity away, it has to increase the distance to the focal plane, you will actually see the front element move outwards. To focus really really close, extension tubes are added to move the lens mount even further away from the focal plane. A primary lens has only 2 or 3 lens groups which is why it can achieve such high resolution and sharp focus. The reason for the extra groups is so that color refraction is corrected, a single lens would not focus red light at the same distance as blue light.a zoom lens has six or more lens groups which is why it does not achieve the resolution of a primary lens.these groups allow focus tracking, internal focus and macro focus in addition to color correction, but at a cost to image quality.