1.They’re escape sequences. n is a newline and r is a carriage return. In Windows most text editors have a newline as rn and on unix it’s n. 2.r is the carriage return n is the newline These are available in many other languages aside from PHP. 3.They’re “carriage return” and “line feed” respectively. Typically on Windows, you need both together to represent a line terminator: “rn” whereas on most (all?) Unix systems, “n” is enough.