What is a prime a triplet??

Prime triplet is a set of three numbers which is of the form (p, p + 2, p + 6) or (p, p + 4, p + 6).

For example,

(5, 7, 11), (7, 11, 13), (11, 13, 17), (311, 313, 317), (461, 463, 467)