A real Persian carpet is handmade in Iran and only natural wool and fibers are used in the process. They are handmade by individual weavers, rather than in factories. Also, Persian rugs are made of all natural wool and silk and do not have synthetic silk or wool.
Most Persian rugs have a cotton foundation, but there are also some carpets that have a silk foundation. These types of rugs are very valuable and are much more expensive than rugs with a cotton foundation.
Typically, a single carpet could take months and even years of complex, detailed diligence to create. Time taken depends on the size and quality of the carpet (the finer the carpet the longer it takes to create). Often times many people would work side by side on the same carpet. Hand Knotted Rugs are the only Persian rugs.
 
All Persian rugs have specific characteristics, such as borders, selvage, field, etc. What distinguishes one rug from the other is the design; one unique aspect of the Persian rugs is their curvilinear designs. Curved-design weavings are much more difficult to execute than geometric ones. Persian carpets made of silk or high quality wool are much more expensive than those made of cotton or materials of lesser quality. However, the rug shows better and lasts longer.
The two most commonly used knots in Persian weaving are the Turkish and Persian knots. The Persian knot is commonly when weaving finer rugs, because it is generally smaller than its counterparts. Wrapping around one warp, then passing behind the neighboring warp so that it divides the two ends of yarn, makes the knot. The Turkish knot is made by passing between two neighboring warps, looping under one, wrapped around both, then pulled through the center - both ends will come out between the two warps. Silk Persian rugs may have more than 1,000 knots per square inch. Knotting techniques are specific to the location where the rug is woven; the design pattern used and even the individual weaving team.
The basic types of Persian rug:
Tribal Weavings - these rugs are usually of primitive design, and possess a limited color range: reds and blues predominating. Tribal weavings are made on a horizontal loom, and usually made of coarse, yarn.
Village Weavings - these rugs often employ a cotton warp and weft which add stability and resistance to shrinkage. The ground colors are often blue and red, but with easier access to modern dyestuffs village weavings now often incorporate lighter and brighter colors such as beiges, gold, and yellows. This category includes some very prestigious and expensive rug types. Persian rug collectors know well that heavy rugs such as Heriz, Bijar, and Sarab are some of the toughest of all hand-made rugs.
 Town Weavings - the finest Persian rugs are all town-woven. They are made on a fixed vertical loom which allows far greater knot density, and a much more consistent weave. These rugs are usually very detailed in their design, and often incorporate complex multiple borders. The colors of town-woven rugs are much more diverse than the coarser rug types.
 Persian carpets are named after the city or the region in which they were made. Among the most popular ones are Tabriz, Bidjar, Nain, Qom, Hamadan, Mud, Meshkin, Mashhad, Kirman, etc. Each region has a unique characteristic and method of making rugs, so take a moment a look up a name on a map to see where the rug is from.
 
Historically, the largest carpet producing centers that flourished in Persia are in Tabriz (1500-1550), Herat (1525-1650), Kashan (1525-1650) and Kerman (1600-1650). The best known of the Tabriz works are the twin Ardabil carpets in the permanent collections of the Victoria and Albert Museum and the Los Angeles Country Museum. The Victoria and Albert Museum in London brought a Persian carpet for 2, 500 British pounds in 1892, and it was deemed too expensive. Today, the "Ardebil Carpet" is well-known and is considered the best carpet on public display. So, Persian carpets are regarded as one of the highest levels of artistic sophistication accomplished by humankind.