Hello Student ,
Oscillatory/Vibratory Motion : it is the motion that repeats to and fro along the same path, about an equilibrium position. Every oscillatory motion is periodic but all periodic motions are not oscillatory.
SHM : SHM is also an oscillatory motion, but here at any point acceleration is directly proportional to its displacement from mean position , but in opposite direction.
For Oscillatory Motion F = -kx^n
n>0 . But for SHM  F= -kx^1 , so for SHM n = 1. Hence in the above question motion is oscillatory but not SHM.