In HMC, under Catalog folder, there is Keywords node (pic attached). What is the function of it? Didn't find any information on hybris wiki.
Please do not mix with "Keyword redirects" feature.
It uses to add meta keyword tag to products/categories. Which help Google SEO. Meta keyword tag is hidden in your code. People on the page will not be able to see them. The search engines still read them for it to have an idea of what your page is about and what exactly your keywords are.
If you see your configured product page source. you can find
<meta name="keywords" content="yourvalue1, yourvalue2, etc">