The impeachment process is a power granted to the legislative branch. This gives the House of Representatives and the Senate an opportunity to get rid of an elected official for wrongdoing.
The impeachment process starts in the House of Representatives. A member of the House must bring formal charges against the individual who did something wrong. From there, the House needs to investigate and vote on whether or not this process should continue. In order to continue, there needs to be a majority vote. If there is a majority vote in favor of impeachment, then it goes to the Senate.
The Senate is responsible for holding the trial, listening to the evidence, and ultimately making a decision. In order to officially remove an individual from office, there needs to be a 2/3 vote in favor of the motion.