Lulu here from the Shopify Support team. Thanks for reaching out here, and I'll be more than happy to help you out.
This would usually be determined by your Shopify admin under "Online store > Preferences > Title and meta description". If you have updated this here then it is up to Google to update this. Google will crawl your store and update any changed meta descriptions and SEO texts.
If you have just recently changed the meta description, or actual page content, it may take Google a few days, or even weeks, before it scans the site again to get the new information. It is possible to ask Google to recrawl the site using these instructions from Google. However, as their guide says, it's not guaranteed, and it may take still take several days to complete.
I hope this helps but let me know if you have any further questions at all.
Lulu | Social Care @ Shopify - Was my reply helpful? Click Like to let me know! - Was your question answered? Click Accept as Solution