In the United States, we have a system of separation of powers. We have a legislative branch that is composed of two houses, the House of Representatives and the Senate. We have an executive branch that is run by a president who is elected separately from the Congress. This allows us to have the situation that we have today where different political parties control different parts of the government.
The US presidency is controlled right now by the Democratic Party. Barack Obama is a Democrat. When the presidential election occurs in November, the Democratic Party will retain control of the presidency if Hillary Clinton wins the election.
Both houses of the Congress are controlled by the Republican Party. Their hold is stronger in the House than in the Senate. It is possible that the control of one or both houses will change after the November elections. Most observers think that it is much more likely that the Democrats could take control of the Senate and much less likely that they could take over the House.
For the time being, then, the Democratic Party is in control of the Presidency and the Republicans have both houses of Congress.