The hobby of collecting includes seeking, locating, acquiring, organizing, cataloging, displaying, storing, and maintaining whatever items are of interest to the individual collector. The scope of collecting is unlimited: "If something exists, somebody somewhere collects them."
The most obvious way to categorise collections is by the type of objects collected. Most collections are of manufactured commercial items, but natural objects such as birds' eggs, butterflies, rocks, and seashells can also be the subject of a collection. Some collectors may collect not a specific type of object, but instead objects with specific properties; for example, some people collect items that once belonged to famous people. Among collections of manufactured items, the objects may be antique, or simply collectible. Antiques are collectible items at least 100 years old, while collectibles can be arbitrarily recent. Collectors and dealers may use the word vintage to describe older collectibles. Items which were once everyday objects but may now be collectible since almost all those once produced have been destroyed or discarded are called ephemera. Philately, phillumeny, and deltiology (collecting postage stamps, matchboxes, and postcards) are forms of collecting which can be undertaken at minimal expense.
Some collectors are generalists with very broad criteria for inclusion, while others focus on a subtopic within their area of interest. Some collectors accumulate arbitrarily many objects that meet the thematic and quality requirements of their collection, others—called completists—aim to acquire all items in a well-defined set that can in principle be completed, and others seek a limited number of items per category (e.g. one representative item per year of manufacture or place of purchase). The monetary value of objects is important to some collectors but irrelevant to others. Some collectors maintain objects in pristine condition, while others use the items they collect.
Collecting is for some people a childhood hobby, but for others a lifelong pursuit or one that begins in adulthood. Collectors who begin early in life often modify their aims when they get older. Some novice collectors start purchasing items that appeal to them then slowly work at learning how to build a collection, while others prefer to develop some background in the field before starting to buy items.
The emergence of the internet as a global forum for different collectors has resulted in many isolated enthusiasts finding each other.