Strong typing is a programming concept where the type of a variable is strictly enforced. This means that once a variable is defined as a certain type, it cannot be used as another type without explicit conversion. For example, if a variable is declared as an integer, trying to use it as a string will result in an error. This helps prevent bugs and makes the code more predictable. In strongly typed languages, such as Java or Python, type mismatches are caught at compile time or runtime, ensuring that operations on variables are type-safe. This contrasts with weakly typed languages, where types can be more flexible, potentially leading to unexpected behavior.