Where in the constitution is the veto power described

In Article II, Section 7.

Explanation:

The veto power refers to the presidential power to disapprove the passing of a bill, order or joint resolution made and voted on by Congress; the US Constitution describes such authority in Article II, Section 7.

Part of the section explains that every bill, order or resolution that the House of Representatives and the Senate make has to be presented to the President before it becomes law. Once the bill is in his or her office, the President can do one of the three following actions: to sign the bill, thereby making it a law, to veto the bill, in such case, the bill has to return to Congress which has the power to override the Presidential veto only if the bill is voted on by two-thirds of each house, or to leave it unsigned and do nothing about the bill, in such case within ten days (Sundays excepted), the bill will immediately become a law.