Once fully developed a feather is a dead matter like your finger nails, though there are still muscles attached the base of each feather which can move each individual feather to help keep it in place. Feathers do not last for ever, they become worn and battered and are replaced regularly by the bird once or twice a year depending on species. Feathers have a basic form of a central hollow supporting shaft called a 'rachis' and a number of fine side branches. These side branches have even finer sub-branches in contour feathers. The side branches in these are called barbs and are linked together by a set of barbules and their hooklets sometimes called 'Hamuli'.
Barbs have side branches of their own called barbules.
The upper ones containing a series of hooklets and the lower ones without hooks but slightly convex in form to catch the hooklets of the barbules from the next barb along the shaft. This is perhaps best understood by seeing the diagram. The gripping effect of any one set of barbule hooklets is not great, but like the threads that hold your clothes together the combined effect is sufficient to keep the feathers together. Playing with any wing feather can demonstrate the affect of these tiny attachments. The overall presence of all these barbs and barbules together is called the vane of the wing.