The definitions of deferred versus immediate payouts in o.m. answer are excellent. The explanation for why the public sector puts more emphasis on deferred payouts only covers the 'nice' aspects though.
Politicians are only humans and not in power indefinitely. In democratic countries often only a couple of years. If you promise say a fireman a mediocre pay right now but a very generous pension later on, he will usually trust the promise and evaluate the offer accordingly. The voter who will have to pay for the pension in some decades unfortunately will not. Shifting the cost of some public service some 20 or 30 years into the future is an excellent vote winner for politicians in a lot of cases. Get the benefit of the spending now but the cost will only kick in when you are long out of power. If people where perfectly rational this wouldn't work but in the real world they are not and it does.
Edit: Quotes were requested in the comments, which will be difficult. Even politicians who deliberately make deals like that will not say so in public. But one can observe various examples in practice where policies were made that have vastly higher cost at some time far in the future then the benefit they give now.
Public American pension schemes are an example. These are vastly underfunded and where so for decades. Nevertheless only now politicians are slowly starting to be criticized for it. Almost all climate policy or more accurately lack thereof can be seen this way.