Question

distinguish between public sector, private sector and joint sector..

Answer 1

public sector is the sector which is under the hand of government which is used for public commonwealty but private sector is a sector which is over the hand of the government
joint sector means in the sector where there is hand of the both.
for ex public sector - railway transportation, etc
private sector-industries

Answer 2

Public sector is under Govt undertaking like Railways
Private sector is under any private body . This bidyay be an individual also like reliance industries
Joint sector is under govt and its partners from other sectors. Mahanagar Gas Limited, Maruti Ydhyog