Hi Jaydeep,
UG denotes undergraduate courses or which is popularly known as bachelors courses. For example, B.Tech, BBA, B.Com which are pursued after 12th. PG denotes to Post graduation which is done after completion of UG or bachelors course. For example, M.Tech, MA, MBA.
Hope this clears things up,
All the best!
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile