Powers and responsibilities
Now, the President of the United States is quite a busy person. He holds responsibilities out the wazoo. The following chart contains his many Chief-oriented titles and duties with some broken English here and there. It's not mentioned, but he also must appoint the heads of executive departments. Of all responsibilities, though, the most important is to ensure that all laws are "faithfully executed."
Some of the president's powers aren't necessarily the most formal. For instance, he must hold and attend press conferences, deliver the annual State of the Union address, act as the head of his political party (as mentioned above), and be portrayed as the primary political power of the Oval Office. That last one isn't much of a power, but it is important and it applies to the president.