When the President of the United States appoints someone to a position, like a Supreme Court judge, it has to go through the Senate for approval. This rule is reflected by the appointments clause in the Constitution.
This clause applies to all of the positions that the president can fill. According to the constitution, the president is able to choose ambassadors to other countries, public ministers and consuls, Supreme Court judges and select officer positions. The Senate routinely has the nominated person testify at Senate hearings or in front of committees. The committees have become standard practice since the mid-20th century. Many of these positions end with the end of the president's term, but there are exceptions like the Supreme Court appointments. These are for life, or until the judge decides to retire.