Private sector refers to business owned and manege by individuals which are not government funded, private sector include business, companies, commercial banks etc which are owned and manege by private individuals who has nothing to do with government for the purpose of profit making
Private sectors can't survive without the intervention of the government, in fact many successful private sectors that you see around today that are successful has their funding one or the other from government individuals and groups but what they do is that they don't operate the companies rather they allowed it to be manage by other people because name matters sometimes in business, some names in a company can make or break a company, some people wouldn't want to have anything to do with a business if a particular person person or group are involved.
The role of private sector in developing the economy of any country is very crucial and important as the role of government in society is for protection of life and property and creating the right environment for business to strive
All over the world it's private sector that has helped the economy of nations, private sector involvement is needed for economic stabilization as government only can't do this alone
That's some of private sector objectives but a private sector can't do alone if the government policy isn't favorable, a government policy determines how far a private sector can go, if government has a high interest rate, many business wouldn't go far because the need for urgent liquidity is going to be a problem due to high interest rate, if the government has high inflation, most business and companies will fold up immediately. I think for private sector to add growth to economy, that depend on the impact of the government to the economy as well.