In the simplest of terms, an artifact is an item that has been enchanted; suffused with aether. While inanimate objects don't produce aether like living creatures do, they can accumulate aether and produce magical effects. When an object collects enough aether to display magical qualities, that object has become an artifact.
There are limitless ways by which an object can become an artifact. But there are three most common methods. First, an object can form naturally (or be cultivated). This is known as a wild artifact. Second, for a mundane item to be exposed to aether or some other source of magical energy repeatedly or for an extended period of time. An artifact created in this manner is referred to as infused. The third method of creation is for a mundane item to be intentionally enchanted.
Naturally forming, or wild, artifacts are typically objects that formed without the hand of a crafter. Naturally occurring crystals or stone formations are a well-known expression of this form of artifact. Artifacts such as these generally need to be found and cannot be made. However, there are wyrd communities that have taken to cultivating these natural artifacts by finding places that one is likely to form and carefully ensuring the conditions are right for an artifact to form. It is slow, tedious work, but the results are well worth the effort to those who embark on this path.
The second category of artifacts, infused, are similar to wild artifacts in that the infused artifact is created unintentionally as the result of an exposure to large quantities of aether. Whether that exposure happens in small amounts over an extended period time or in a large amount all in one cataclysmic event; the item exposed is forever changed. The simplest example of this form of artifact is a family heirloom that develops mystical qualities from generations of being held and kept close at hand. These sorts of magical items often also develop personalities in the process of their inadvertent creation.
The third form of artifact is perhaps the most familiar to mortal society; artifacts created by enchantment. Enchanted items are imbued with magical energy and designed to serve a particular purpose. These items generally don't develop a consciousness and only work for the purpose they were enchanted for. Items of this nature are most commonly simple tools or weapons.
Infused and enchanted artifacts are by far the most common encountered in mortal society. Wild and infused are more common among the wyrd.
In the times since the Disenchantment, fewer artifacts have been produced. Most artifacts encountered by collectors are ancient and the story of their origin and intended use have been lost to time. But since magical items were produced in such high volumes in the past, it's still much easier to find an older artifact than it is to lay hands on a modern one.
Most magical items produced in modern times are products of wyrd crafters. The art of creating artifacts has been largely lost to mortal crafters. There are only a handful of mortal workshops that continue the tradition of aetheric crafting and they only produce a handful of new artifacts in a given year. Their work is highly sought after by mortal collectors and magicians. This makes acquiring an example of their work next to impossible for most.
The most well-known process for modern artifact creation is that of the mortal artisans who work as part of the reclusive Chamfarao's workshop.
The team begins with a bespoke object, usually produced by one of the in-house artisans. Once they have the object they intend to enchant, formulas are drawn up for the magical effects the artifact should produce. The formula must be customized to the object for the enchantment to properly attach to the item. Once the formula is complete, then the it is bound to the object by use of a combination of ritual and skilled crafting. A variety of tools previously enchanted to make the work easier such as engravers, awls, inks, chisels, and needles can be employed to help finalize the enchantment.
But in the end, there are nearly as many methods of fabricating artifacts are there are artifacts. And this is a largely mortal-centric summary of the topic.