There are three branches of government: the Executive branch, Legislative branch, and Judicial branch.
The Legislative branch is the branch of Congress, which is made up of the House of Representatives and Senate. Their main responsibility is to create laws. They also have the power of impeachment towards the President and can override vetoes with 2/3 the majority vote. The can also approve of federal judges.
The Executive branch is the branch that the President works in, along with the Executive and Cabinet departments. It also has independent government agencies. Their main responsibility is to enforce the laws that the Legislative branch creates. They have the power to veto bills that they make, and can also appoint judges and pardon power in the Judicial branch.
The Judicial branch is the branch of the Courts. It is made up of the Supreme Court, the Courts of Appeal, and District Courts. Their main responsibility is to interpret the laws that the Legislative branch has created. They also have the power to declare presidential acts as unconstitutional, and can declare laws as unconstitutional.
The three branches of the government are the executive branch, judicial branch and legislative branch. Their duties and responsibilities are:
1) Executive Branch: The executive branch is headed by the President in all forms of democracy. The president may be elected directly by the people (US democracy) or by elected representatives of the people (India, etc.). The president is both Head of State and Head of Government in the former system, while in the latter he/she is only the Head of the State; in either case he/she is Commander-in-chief of all the armed forces. The responsibilities of the executive branch include implementing and enforcing laws, appointing the head of various federal agencies, etc. The Prime Minister (if applicable, as in India or UK) and the cabinet carries out the day-to-day operation of the executive branch. These duties also include commanding the armed forces, acting as the state's representative while meeting International powers, etc.
2) Judicial Branch: The judicial branch is headed by a Supreme or Federal Court and also contains other lower courts. The judicial branch is responsible for evaluating the laws formed by the government. Their duties include interpretation of the constitution, review of laws and deciding matters related to the state's affairs.
3) Legislative Branch: The legislative is composed of (at the national level) the senate or parliament and at state levels of state legislatures. Their main responsibility is to make the laws to govern the country. Their duties also include managing the affairs of state including finances, foreign affairs, law and order, approving treaties, etc.