What does the Quick Add means on Snapchat I find it annoying?

I don't want my cousins to see my friends from Quick Add WTH

I already hate Snapchat I made one because people here are crazy about it and there's some interesting famous snappers.

I have nothing to hide but my cousins don't deserve to see my story
What does the Quick Add means on Snapchat I find it annoying?
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