Some people throw things away because they are old. Others spend thousands of dollars to acquire old things. Knowing what makes something an antique is useful information: you won't get rid of valuable items by accident or get tricked into paying too much for something that purports to be an antique.
In 1930 the United States legislature determined that an antique is anything older than 100 years. This was decided so that the customs officials could assess whether an item brought into the country qualified as an antique for duty-free import. Old things that were newer than 100 years are considered collectibles instead of antiques.
If the owner of an antique knows the item's provenance, the value may increase. Provenance is the history of the antique including who owned it, who made it, and where it has been from the time it was made until now. Sometimes provenance is documented in writing. Sometimes it is oral information passed down in a family.
Before repairing broken antiques or polishing or refinishing them, know whether the supposed improvement will detract from its value. Furniture tends to be more valuable if it has its original finish. Oil paintings, on the other hand, can increase in value with a good cleaning by an expert. No matter what type of antique you have, do research before changing it.
Reproductions and fakes abound. Before committing to purchase an expensive antique or collectible, it is a good idea to obtain a written appraisal from an expert. This appraisal is also an important factor to consider when you purchase insurance for the antique.
Most types of antiques and collectibles have been cataloged in reference guides. These books usually include a picture or photograph of each item. They also give information about the history of the items, how many are known to be in existence, where these are, and how much they are worth, depending on their condition.