What is a special character that takes the place of another character called?

A special character that takes the place of another character is known as a wildcard. Wildcards are commonly used in computer applications, especially in searching and querying databases, to represent one or more unspecified characters. For example, in a search operation, using a wildcard allows users to find matches for partial strings or variations without needing to specify every character explicitly.

This functionality is particularly valuable in scenarios where the exact format of the data is unknown or may vary. In contrast, placeholders serve to indicate where information should be inserted, but they do not carry the same flexibility as wildcards. Similarly, substitutes and variables have different applications, focusing more on representing specific values or elements within a particular context rather than matching patterns in searches. Therefore, the term "wildcard" accurately describes a character used to represent unspecified data in a variety of informational contexts.