Squint is a situation where the 2 eyes are not aligned. While one eye looks at the object of regard with its most sensitive part of the retina- the Fovea, the other eye doesn't. A less sensitive, extra foveal portion looks at the object. And this eye looks deviated on external appearance.
As a less " powerful" portion of the deviated eye competes with the most sensitive " Fovea" of the sound eye, the squinting eye tends to get "suppressed".
As the images of the 2 eyes are out of sync',the resulting vision will be uniocular, that is 2 planar, in other words there will be loss of binocular vision and loss of advantage of having 2 eyes.
Squint can be sometimes corrected with glasses. All that may be needed is a detailed evaluation by a paediatric ophthalmologist. Sometimes patching therapies are required for encouraging vision development in the lazy eye.
Surgical corrections also are available when the above doesn't suffice. Early corrections help in better binocular visual function recovery.
Rarer forms of squints are due to limited eyeball movements, that may be due to nerve palsied, muscle problems, acquired due to injuries etc..