I assume you mean the Second Continental Congress, as there were two. The Second Continental Congress was responsible for supervising the Revolutionary War. It was the Congress which authorized the issuance of the Declaration of Independence, and appointed George Washington as Commander in Chief. After Independence, it adopted the Articles of Confederation which was the first truly National government of the United States. Although there was a President of the Congress, there was no President of the United States, nor any judicial branch. It is important to remember that at this time, the states were jealous of their sovereignty and independence, and were very reluctant to grant the Congress much authority. It had the authority to conduct foreign relations and make treaties; but could not tax nor regulate commerce between the several states. In order to finance the war, the Congress authorized the printing of "Continental Dollars," which were virtually worthless. A common phrase at the time was "not worth a continental. It was the restrictions placed on the Congress and the Articles by the States that made it unworkable, and led to the call for a "more perfect union."
The job of the continental congress was to serve as a governing body among the 13 colonies in order to overturn the different impositions that the English had bestowed upon the colonies in an unfair manner.
The idea of the continental congress was conceived by Benjamin Franklin but it was not very popular. However, after the events that occurred at the Boston Tea Party there came a resurgence in the need to advocate the rights of the colonists, and so the group was formed.
The advantage of the continental congress was that it was one of the first steps towards the colonist's process of independence. Although the purpose of the congress was NOT to push for the revolution, it was one of the first instances in which the colonies became united as Americans. Each colony sent delegates and the combination of great thinkers, as well as the planning for the defense of their rights, must certainly have instigated the thought process of the colonies and made them more powerful of their own capacities as a future nation.
The job of the Continental Congress was, basically, to run the United States. The Continental Congress was the only government that the US as a nation had from 1774 until the creation of the new government under the Constitution in 1789.
During this time, Congress acted as both the legislative branch and the executive branch -- there was no real separation between these two branches until the Constitution created the new system. Because the Congress was the whole government, it faced a number of challenges (facing those challenges was its job).
For example, the Congress had to raise money to fund the Revolutionary War and had to try to direct the war. It had to try to get support from other countries like France for the war. Once the war was finished, it had to get the new country started. It had to try to get the states to all work together as a unified country. This was very hard to do as the states had never thought of themselves in this way.
Overall then, the job of the Continental Congress was to act as the whole government for the United States from 1774 to 1789. In doing this, it had to deal with the difficulties of winning independence and then creating a new nation.