Crocodile locomotives were electronic locomotives manufactured in the first half of the last century, originally in Switzerland.
As well as building the train itself, the set builds a section of track and includes two minifigures along with a display plaque.
In order to make the train run, collectors need 88009 Hub and 88013 Technic Large Motor. The set includes instructions for adding the components, then the Powered Up app is required to operate the motorised train.
Here is the official product description:
Inspired by the Class Ce 6/8 II locomotive, first built for the Swiss Federal Railways between 1919 and 1927, this beautiful LEGO® model is packed with realistic details. With side rods that move as the wheels turn and posable pantographs that move up and down, there’s lots to explore. Lift the roof to access the crew compartment and use the 2 minifigures to bring the story of this iconic train to life. Add the Powered Up components (sold separately) to motorize your locomotive.