After selling us knock down furniture for many years now, we can finally buy that special connecting hardware ourselves.
There are two basic types: sunken nuts, and cams.
The principle of a sunken nut, as you see in the first photo, is that you have a little cylinder that has a threaded hole through it. Because the 'nut' is in the form of a cylinder it allows you to drill an easy round hole from the side and then simply slide this nut into the hole. A slot is used to line up the threaded portion with the bolt. Then a bolt, usually with a hex socket and a very flat head simply fits through the front piece and on down past the nut. This is an ideal attachment feature for particle board and plywood because there is no holding force that is trying to split apart the panel, like you do get when you drive in a wood screw.
The cam action units are designed to give you removable but almost hidden joinery. As in the second photo, a mushroom shaped stud is screwed into the edge of one panel. The face of the other panel, often a drawer front, has the receiving mechanism. This will always be in a cylindrical form to allow for easy drilling of the receiving hole. Most of them screw into place or have some expansion mechanism that holds them tightly into the hole.
Notice that forcing outward in a hole drilled in the face of a panel does not tend to split the panel, so considerable grip can be used here. The mushroom head goes into the receiving hole and a little screw drives a cam action that pulls the mushroom head tightly into the joint. With any of the cam action connectors, you have to get your dimensions very close as there is rarely much tolerance on the draw of the cam. In a factory, the precision drilling required for all of these connectors is a simple jigged process. When working at home, make sure you have exactly the proper drills for a proper fit, which are often metric. Make drilling guides, even out of scrap wood, but something that prevents your drill from wandering or going in crooked.
This is wonderful hardware, but it is not very forgiving to lineup errors.