structural:summarization
Types of collection

The most obvious way to categorize 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. For some collectors, the criterion for inclusion might not be the type of object but some incidental property such as the identity of its original owner.

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 or completionists —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). Collecting items by country (e.g. one collectible per country) is very common. 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.