"_": A symbol used to represent a blank or missing letter, word, or space in a text or puzzle. It is often used as a placeholder or to indicate that something should be filled in or completed.
"Underscore": A term commonly used in computer programming and typography to refer to the underscore character (_). It is a horizontal line positioned below the baseline of a font and is often used to separate words or replace spaces in file names or variable names in programming languages.