Child Theme confusion

I have a site built on a child version of the Astrid “parent” theme, which I’ve customized. The parent Astrid theme has an update available.

If I update the parent Astrid theme, how does that affect my child theme? Will I lose my customization? Nervous about that. I know a child theme is the way to go for customization, but I’d just like to make sure I understand what’s going to happen to my site before I do the parent update Thanks in advance for any help!