‘Best losers’ guaranteed seats in Parliament

In his dialogue with NTU students, Chok Tong told them that our Constitutions have been tweaked to guarantee that the ‘best losers’ in a general election will still get to Parliament. At present 9 seats were provided for the losers.

Is this a concession, a grace or an effective alternative to having opposition members in Parliament? What is the purpose of having oppositions in Parliament?