It is just the name for the value. But its value cannot be change in the entire script once it is created. Generally its name starts with either letter or underscore (no other signs)
Define (name, value, case-sensitive)
Name: It specify the name of constant
Value: It specify the value of constant
Case-sensitive: It means whether the value of constant is case sensitive or not. Default it is false.
Define(“AMAZING”, “paris is beautiful city”);
Paris is beautiful city