The Middle Ages encompasses the time from the Fall of the Roman Empire in 400 CE until the beginning of the Renaissance, around 1500 CE.
Clothing of the Early Middle Ages, or Dark Ages, was basically a tunic and under tunic, both sewn from a cross shaped piece of fabric that was folded and hand stitched. Later, the tunic was cut in two pieces, then four piece for a better fit.
Peasants and serfs made their clothes at home of wool and hemp. The shearing, and cleaning of the wool; the spinning, and weaving was a long drawn out chore before the invention of the spinning wheel and the horizontal loom. But the garment were durable and long lasting. One garment could last a life time.
While the upper classes and aristocracy wore basically the same type of clothing, their under tunics were made of linen which was made for them by workers. Upper class women sewed tunics at home and some were made by professional tailors.
Due to the loss of trade that followed the end of the Roman Empire, trade was minimal, so the importation of fine fabrics was expensive and rare. But finer weaves, borders, and embellishments made for better clothing for the elite.
After the invention of the horizontal loom and spinning wheel, the manufacture of clothing became easier. These technological improvements made finer clothing more available and affordable. The Crusades introduced silk, damask, and other luxurious fabrics and designs into Europe. And when Marco Polo's adventures heralded a new interest in the Far East, trade increased, creating greater availability of textiles, design ideas, and new patterned fabric to Europe.
Clothing worn by the nobility and merchants began to change, introducing the concept of fashion. While the Church dictated certain aspects of dress for modesty, such as veils for women, alterations in the in the types of fabrics used varied the styles that became popular. Women wore veils made of sheer muslin, interwoven with golden threads. Gowns became more ornate with variations in the neckline, sleeves, and hem lengths.
The establishment of guilds and improvements in the manufacture of clothing created an upwardly mobile middle class able to emulate the clothing styles of the upper class. New styles emerged including the elaborate head dresses of the later Middle Ages. The head dresses that looked like horns were wildly popular for a generation, as was the classic fairy tale princess style of hat called a hennin. A hennin was a tall, conical hat worn with a veil, a style much identified with the Middle Ages.
The later Middle Ages saw women's gowns grow trains, and sleeves elongated so that long flaps reached the ground.
The changing of style and middle class interest in emulating the clothing styles of the elite created what we think of today as fashion.