Vintage clothing is a generic term for new or second hand garments originating from a previous era. The phrase is also used in connection with a retail outlet, e.g. "vintage clothing store." It can also be used as an adjective: "This dress is vintage."
The word vintage is copied from its use in wine terminology, as a more elegant-seeming euphemism for "old" clothes.

Definition

Generally speaking, clothing which was produced before the 1920s is referred to as antique clothing and clothing from the 1920s to 1980s is considered vintage. Retro, short for retrospective, or "vintage style" usually refers to clothing that imitates the style of a previous era. Clothing produced more recently is usually called modern or contemporary fashion. Opinions vary on these definitions.
Most vintage clothing has been previously worn, but a small percentage of pieces have not. These are often old warehouse stock, and more valuable than those that have been worn, especially if they have their original tags.

Purpose

Although there has always been some demand for old and/or second hand clothing, the awareness, demand and acceptance of this has increased dramatically since the early 1990s.
This increase in interest is due in part to increased visibility, as vintage clothing was increasingly worn by top models and celebrities, e.g. Julia Roberts, Renee Zelwegger, Chloe Sevigny, Tatiana Sorokko, Kate Moss, and Dita von Teese.
There has also been an increasing interest in environmental sustainability in terms of reusing, recycling and repairing rather than throwing things away.
A resurgence of historically based sub-cultural groups like rockabilly and swing dancing has also played a part in the increase in vintage clothes.
Other reasons that some people are attracted to vintage clothing include:

• Unique or almost unique: most items were custom made, and others were manufactured in small quantities only.
• Good quality: they were designed to be worn for years and passed on to other family members, so they were made of robust materials, well cut and well made, with generous seam allowances and hems which allow for alterations and custom fit.
• Fine materials: many of the unusual older fabric types are no longer manufactured, or are now prohibitively expensive.
• Value for money: garments generally sell for a cost far below similar new modern garments.
• History: an appreciation of the past, the roles of previous generations and the skills of respected designers.
• Detailing: hand finishing, unusual buttons, hand embroidery, handmade lace, crochet, applique, beading and other techniques.
• Style: vintage clothing has traditionally been the favourite of creative personalities because it offers an enormously wide range of imaginative styles.
• Investment: some people buy to collect rather than to wear, and increasingly, good quality vintage garments especially items by well-known designers are sought after by collectors.
• Low Carbon Footprint: some people buy vintage clothes because it is less demanding of world resources.
• Union made: many vintage clothes carry a union label, thus avoiding labor practices in third world countries that are regarded as abusive.

Source: http://en.wikipedia.org/wiki/Vintage_clothing