In its broadest meaning, the word “vestments” simply means clothing. In a narrower sense, it means clothing worn by a special group for a special purpose.
The ordained ministers of God are men set apart for a special calling. Every religion in every age and culture has thought it fitting that the clothing of priests and ministers should denote at all times their special calling. Thus it is that Anglican and other priests of the Western Catholic Church have long worn a distinguishing garb even in everyday life. This garb is a black suit and a gray suit, or some combination of the two, with a plain white, round collar of several types. This dress marks them as men apart, and makes their calling and status readily identifiable. Their calling is not that of a nine-to-five worker, and as identifiable priests they are available in all sorts of physical, moral and psychological emergencies as they move about in our society.
In a still narrower sense, vestments are the special garments worn in the conduct of Divine Service. The basic and simplest form of this garb is the long black gown known as a cassock, over which is worn a white surplice. A priest wears a stole around his shoulders, hanging free in front. A Deacon, whose garb is otherwise the same, wears his stole over his left shoulder with the ends fastened together under the right arm. (It may be noted that choir members and servers or acolytes may (and often do) wear similar garb, except for the stole, and that their surplice is called a cotta, being considerably shorter than that of the clergy).
It is widely customary in Anglicanism for the garments described above to be worn at all Services, whether of the Offices, the Eucharist or other celebrations. However, many Anglican clergy wear a more complicated and elaborate set of vestments when celebrating the Holy Communion. These consist of a white alb (with a robe girdle holding down the stole), a neck cloth called an amice, and the chasuble, a large oval sleeveless garment usually highly decorated with embroidery, representing the royal robe which the Roman soldiers mockingly put on Christ after they had scourged Him.
Bishops, of course, have certain distinctive garments such as the rochet, a long white linen garment, which in Anglicanism is traditionally styled with full sleeves having bands or ruffles at the wrists. This is worn over the cassock, and over it in turn is worn the chimere, a black or scarlet sleeveless gown. On certain occasions, and at certain points in a service, the bishop wears a distinctive headpiece called a mitre, symbolic of the helmet of salvation spoken of in Isaiah, and by Saint Paul in his Epistle to the Ephesians. Anglican bishops wear a mitre which is shorter and more angular than those worn by Roman Catholic bishops.
In procession and on occasions of high ceremony, the clergy may wear copes, long capes of rich and colorful materials.
Lay readers, however, are garbed in cassock and surplice (wearing no stole, which is reserved for the ordained clergy), and may also wear an academic hood of the college and degree appropriate to the individual lay reader.
These are the basic and traditional vestments. Whether the norm is to use only the simpler ones, or to use the more elaborate ones for celebrations of the Holy Eucharist, will depend largely on the wishes and custom of the priest and parish. No overriding importance attaches to this choice. The services and Sacraments of the Church are entirely valid and efficacious in any case; indeed they would be so if no vestments at all were worn. Yet tradition plays a meaningful role, and adherence to it makes for decently and orderly conducted services. Vestments add to the solemnity and dignity; and, where the more elaborate Eucharistic vestments are used, there is undoubtedly a richness and pageantry altogether appropriate to the worship of Almighty God.