Implicit data type conversion, also known as type coercion, occurs when a programming language automatically converts one data type to another without explicit instructions from the user. Converting a varchar to char is an example of implicit type conversion because both are string types, and the system can easily handle this without explicit user intervention. A varchar is a variable-length character string, and char is a fixed-length character string. Thus, converting varchar to char can be done implicitly by the system. Other conversions listed, such as date to char, char to date, and char to timestamp, typically require explicit conversion functions because these involve different data types with more complex structures.