This is a natural nylon knock-on nut for predominantly wood assemblies. Indeed, it makes it possible to solidify your assembly and to ensure that it does not move. It is ultimately a plastic insert to push in or glue.
These are parts to be used for regular assembly and disassembly.
These plastic inserts provide a slight pull-out force and are recommended for all materials.
This piece is very often used especially by kitchen designers. For optimal fixation, it is recommended to first introduce wood glue into the hole and then insert the socket.