A wildcard is a symbol, character, or string that represents one or more unknown or variable values in a specific context. It is often used to:

1. Match patterns in search queries, regular expressions, or file names.
2. Replace unknown or missing information in a dataset or database.
3. Indicate a flexible or dynamic value in a programming language or script.

Common wildcard symbols include:

- Asterisk (*)
- Question mark (?)
- Percent sign (%)
- Underscore (_)
- Dot (.)

For example, in a search query, "j*smith" could match names like "johnsmith", "jasmith", or "jasonsmith". In a database, " '%' " might represent any value in a field.

Wildcards simplify searches, queries, and programming tasks by allowing you to specify flexible criteria or placeholders for unknown values.