When we can't simplify a number to remove a square root (or cube root etc) then it is a surd..
Example: √2 (square root of 2) can't be simplified further so it is a surd
Example: √4 (square root of 4) can be simplified (to 2), so it is not a surd!
22/7 is not a surd ,it is just approxiate value of pi not exactly pi.So 22/7 is not a surd(it is just a rational no)
but pi is actually 19th root of 2791563950 . So, it is an irrational number and the result of a surd.