Question

what is this symbol befor and after x refers to plz explain.

Answer 1

Modulus is the symbol used before and after the x, to indicate the positive value of x.

Whenever we use mod, then the negative values become positive and positive remain positive.

Answer 2

it is modulus
if the value of x is negative then while removing modulus it becomes positive
and when the value of x is positive it remains same when u remove modulus