A side trip, usually short, made with the intention of returning to the starting location.
a journey taken for pleasure; "many summer excursions to the shore"; "it was merely a pleasure trip"; "after cautious sashays into the field"
wandering from the main path of a journey
a packaged day trip off the ship to a point of interest, which you will pay a fee to enjoy
A side trip from a main destination, usually at added cost and optional.
An excursion is a trip, usually made for leisure or educational purposes. It is often an adjunct to a longer journey or visit to a place, sometimes for other (typically work-related) purposes.