What is the difference between a senator and a governor, and which is higher in rank?

If you're speaking of the difference in US terminology. A governor is the head of a single state. A senator is the state's representative in the Senate. Each state has two senators, between one and 50 representatives in the House, and only one governor. The governor is the head of a state's executive branch of government, senators are part of the federal legislative branch, and thus neither one really "outranks" the other.

Though this much should be said: In state affairs such as state laws, the governor is the top of his state's chain of command (and answers only to the President).

A governor is a person elected by the people of a state to be the top leader in that state. They have many of the same powers that a president have, but only on a state level. They can pardon criminals prosecuted by the state, they can sign and veto bills passed by the congress of the state. They can appoint people to certain positions, and they speak for the state on matters regarding the state.

A Senator, is one of two elected by every state. A Senator represents their states constituency by making and voting on laws that are created by congress. Some Senators also serve on various committees.

Many Senators and Governors during their term aspire to hold the office of the President of the United States. However, there is nothing in the Constitution that says that the President must be a Governor or a Senator. The constitution only says that the President must be a citizen of the United States and must be at least 35 years old. Experience is not mentioned. However the public believes that someone with government and/or military experience is better than someone without such experience. This is why you see a proliferation of Governors. Since Governors have many of the same powers as a President, but on the state level, the US has elected many governors to the position of President (i.e., George W. Bush, Bill Clinton, Jimmy Carter), but Senators have also become president (Richard Nixon after being VP and JFK)

George Washington and Dwight Eisenhower were both military leaders who became president.

Regarding rank, it's like comparing apples and oranges. The senators are involved with the federal government while the governor is head of his state government.

Generally, being a governor from a wealthy and populous state would be more prestigious than being a junior senator from a state with little clout, whereas being a U.S. Senator from any state would be more prestigious than being the governor of poor or sparsely populated state.

The senators are ranked among themselves according to seniority. The President Pro Tempore of the Senate is the most senior senator of the majority party.

The Senate is actually the American version of a council of elders.

Simply stated, a governor is an "executive." A senator is a legislator, not an executive. A governor at the state level is comparable to the President at the national level in that both are heads of the "executive" branch, much like a CEO is for a company.

A senator is a legislator, not an executive. They are responsible for representing the people of their state in the legislative process. Constitutionally, they are not authorized to "execute" the laws. A Senator is comparable to a Representative, except that there are only two senators per state reguardless of the population. The number of representatives is based on the population of their state.

Constitutionally, one could argue that since the governor is the highest authority in the state, they would be higher in rank. Likewise, if a senator left office prematurely, the governor has the authority to appoint a replacement until the next election.

Considering the aforementioned, governors "usually" make better presidents because they have executive experience in government. This is not to say that a senator could not be a good executive; just that their executive experience as a senator does not in any compare to that of a governor.