What is the difference between a tourist and an excursionist?

A tourist goes to a specific location to see specific things. Like a visit to Paris to see the Louvre. Also, a tourist will usually stay overnight and sleep in the location he is visiting.

An excursion is a short trip, just for pleasure. Like a hike in the woods or a walk in the park. Also, an excursionist will usually go back to his/her town, hotel or residence that it is different from the visited destination, when sleep/rest is needed.

A tourist is one that makes a tour for pleasure or culture.

An excursionist is a person who goes on an excursion.

An excursion is a usually short journey made for pleasure; an outing.