New to Figma. Please help!

Hey guys. I’ve using Figma for only a month now and still figuring things out but there are some problems that I just can’t figure out on my own.
I work as a UX/UI designer and I have to use the design system that designer who worked before me made. Now I need to add new things to the design system but here is the problem.

스크린샷 2021-06-07 오전 11.55.33

does anyone know what that stroke is? around the icons?
seems like some kind of guide line since is doesn’t show when I play the prototype.
what is it called and how do I create?
please help. Thank you!

This is a Slice. They can be used to export a part of the design. But I’m not sure why it is used here since you can simply add export settings to the component itself.

One note: in the future, please make the name of the topics more clear. Without opening your topic it now isn’t possible to know what you are asking. Instead of “New to Figma. Please help!” (meaningless title) you could write “What is this dashed stroke object?” (the question is clear from the title).

Thank you so much!!!