Hi Olliver,
there are no arrays, per se, in Outsystems.
what exactly are you looking for ? There are lists for holding more than one item of the same type. That type can be basic type or a complex type like a structure or an entity or a record
There are both on client side and on server side some built in actions available to manipulate lists, like finding position of an item, filtering, sorting, ....
Many parts of the platform, like certain UI widgets, but als aggregates and sql widgets to retrieve data from the database, all work with these lists.
This you will all learn in the beginner courses.
Dorine