For this question I'm assuming a utterly infeasible technological breakthrough suddenly makes wormholes technology possible. However there is a major catch, the 2D "windows" as they're called don't allow through matter or gravitational pull. The "windows" can be opened for about a half a million USD. Once opened these portals stay open indefinitely unless closed.
Opening a portal requires a large amount of energy, and the use of expensive and bulky machines on one end of the wormhole, with only a small machine and energy on par with a car battery required on the other end. The portals are flat windows that look like portals, however were you to walk up to one you would pass through it unaffected. The portals size can be as small as a millimeter or as large as 2,600 meters, any larger would require using multiple portal machines and linking them together. A portal can have any shape with the smallest definition being a millimeter, however portals are totally flat. Each side of the flat portal corresponds to a side of the other end of the portal. Each of the two connected portals must be the exact same shape and size.
Portals will continue moving as the machine that created them was, at the moment it created the portal, other than controlling its initial motion you can't move portals except as detailed below. This means if the machine was orbiting the earth the portal will continue this motion, even though it isn't itself a object and has no mass. Portals also continue accelerating or decelerating as the machine was when it created it, however while portals can continue accelerating indefinitely they will slow acceleration such that they approach, but never reach the speed of light.
A portal on earth will not slowly drift, since slight changes in planetary motion such as the lengthening of days is effectively counted as deceleration thus the portal undergoes the same slowing, this only holds true for motions that continue at the same rate of acceleration/deceleration as when the portal was created. The end of the portal which requires the expensive machinery to create can be kept linked to the machines so that it moves with them, however this means you can't use those machines to make further portals.
Weapon note: To prevent the scenario of potential apocalyptic destruction, due to someone launching a portal through the sun. I have decided that a wormhole will collapse if more than about the equivalent of a kiloton of TNT worth of energy tries to pass through it in a second, though most energy that can pass through it in a second is equivalent to a ton of tnt. Since the portal only allows through at most a ton of tnt, any additional energy is reflected back when it hits the portal. This is still a lot of energy so it still has a lot of weapon potential. Keep in mind, as far as I know all energy would be in the form of photons.
TLDR: It's a portal that only lets light through.Well actually other details of it are more complicated, so read the whole question before answering.
What uses would be implemented for such a technology assuming it essentially appeared in our world overnight?
The most obvious thing I can think of using it for is as a source of near infinite energy, you could get one end of the portal in an orbit much closer to the sun and use the energy to boil massive amounts of water (also may be useful for desalinization). Using it to allow faster than light communication is an obvious application as well (though given our current technology that's not super useful).