What is the style of writing where spaces are replaced by the underscore character and everything is in lowercase?

The correct answer is distinguished by its specific format where spaces between words are replaced by underscore characters and all letters are in lowercase. This style provides clarity in programming and database contexts where spaces are not permissible, allowing for more readable code or identifiers.

This style is commonly used in various programming languages and database naming conventions, particularly where it's important to convey clear, human-readable names while adhering to syntax rules that require avoidance of spaces. While the name "underscore case" might imply the use of underscores, it is essential to recognize that it is specifically the combination of this character use along with the lowercase format that distinguishes it.

Other naming conventions like CamelCase and PascalCase involve capitalizing the first letter of each concatenated word and do not make use of underscores at all. For instance, CamelCase starts with a lowercase letter (e.g., myVariableName), while PascalCase starts with an uppercase letter (e.g., MyVariableName). These formats serve different purposes and are used in distinct contexts compared to the highlighted style.