In political parties, the Central Committee (also called Steering Committee or National Committee) is a group of party members that make all decisions for the party.
The Committee is usually led by a Chairman. The Committee usually elects it's Chairman to represent it, and also elects other important members of the party.
In one-party dictatorships, the Central Committee is all-powerful and leads the country. In the Soviet Union, for example, Joseph Stalin, used his power as General Secretary to have complete control over the Communist Party of the Soviet Union's Central Committee and was able to become more powerful than the Committee itself.