It is a struct (a bunch of variables) that someone created. It’s not a part of the engine. What are the chances you skipped a step in the tut? If it’s not a tutorial, and you’re just researching, you can create a struct yourself and populate it with data you need. Follow the link above, and look for Using Custom Structs section.
The screencap is from the tut, right? Can you show how it looks like on you side. Perhaps you’re trying to assign it as the Key rather than Value which would not work in a Dictionary Map.
But it’s most likely what I mentioned initially. I’m assuming here the struct will hold a bunch of statistics, right?