Solar panels need the Sun. As easy as that. And they need "to see" the Sun right above them. As soon as the Sun light is no longer hitting the surface perpendicularly the yield decreases. A 3 kW home installation that gets to the peak at noon will probably generate some 2W at sunset and at dawn.
Industrial plant use sophisticated electronic and mechanical systems to move the panels as the SUN moves to keep them, as much as possible, perpendicular to the incoming light.
In the residential installations you get far less power than what you might produce, in the industrial installation you face high installation cost and high operational cost.
The concentration system is made up of two parts. The first, towards the Sun, is composed by a myriad of lenses, a cheap array that focuses light beams coming from many directions thus increasing the quantity of light going through the layer.
Under this layer a special glass can multiply the focus 500 times by using two sheets of reflective materials covering its front and back concentrating at the edges the light captured on all its surface. Once a beam of light has reached a sufficient intensity it will heat the reflective (inner) layer in a specific point and this turns the reflective surface into a transparent one and the light beam will hit the conversion material at exactly 90° since that is the angle where the intensity is max.
Quite simple as an idea although I expect it was quite difficult to make it work in practice!