Is the word tour a noun?

Yes. It can be. It means a journey for pleasure or education; an excursion.

* He's on a year-long tour of Australia, going from city to city and giving concerts.

It can also be a verb meaning travel for pleasure or education; or make a journey for pleasure or education

* They’re touring Canada in a campervan in the summer.

* We toured all the historic battlefields on the bus trip.