The dynasty had a crucial role in the formation of the French state. Initially obeyed only in their own demesne, the Île-de-France, the Capetian kings slowly but steadily increased their power and influence until it grew to cover the entirety of their realm. For a detailed narration on the growth of French royal power, see Crown lands of France.
Members of the dynasty were traditionally Catholic, and the early Capetians had an alliance with the Church. The French were also the most active participants in the Crusades, culminating in a series of five Crusader Kings – Louis VII, Philip Augustus, Louis VIII, Saint Louis, and Philip III. The Capetian alliance with the papacy suffered a severe blow after the disaster of the Aragonese Crusade. Philip III's son and successor, Philip IV, humiliated a pope and brought the papacy under French control. The later Valois, starting with Francis I, ignored religious differences and allied with the Ottoman Sultan to counter the growing power of the Holy Roman Empire. Henry IV was a Protestant at the time of his accession, but realized the necessity of conversion after four years of religious warfare.
The Capetians generally enjoyed a harmonious family relationship. By tradition, younger sons and brothers of the King of France are given appanages for them to maintain their rank and to dissuade them from claiming the French crown itself. When Capetian cadets did aspire for kingship, their ambitions were directed not at the French throne, but at foreign thrones. Through this, the Capetians spread widely over Europe.
The name of the dynasty derives from its founder, Hugh, who was known as "Hugh Capet". The meaning of "Capet" (a nickname rather than a surname of the modern sort) is unknown. While folk etymology identifies it with "cape", other suggestions suggest it to be connected to the Latin word caput ("head"), and explain it as meaning "chief" or "head".
Historians in the 19th century (see House of France) came to apply the name "Capetian" to both the ruling house of France and to the wider-spread male-line descendants of Hugh Capet. It was not a contemporary practice. The name "Capet" has also been used as a surname for French royalty, particularly but not exclusively those of the House of Capet. One notable use was during the French Revolution, when the dethroned King Louis XVI (a member of the House of Bourbon and a direct male-line descendant of Hugh Capet) and Queen Marie Antoinette (a member of the House of Habsburg-Lorraine) were referred to as "Louis and Antoinette Capet" (the queen being addressed as "the Widow Capet" after the execution of her husband).