A tag in a geocoder is a keyword or label that is associated with a specific location or feature. It can be used to refine or filter search results, making it easier for users to find the location or feature they are looking for. For example, a geocoder with a tag system might have tags for "restaurant", "park", "school", etc. If a user searches for "park", the geocoder will return a list of all locations that have been tagged as "park".

For example, let's say you have a service that provides information about tourist attractions. A geocoder can be used to search for attractions, but it can be difficult to find the specific attraction you are looking for. By using tags, the user can filter the search results by attraction type, such as "museums", "monuments", "parks", etc.