New to this - what is sitemap look?

It's just a list of your URLs in XML. Each page sits in a url block with a loc tag holding the address, and sometimes a last-modified date. Add /sitemap.xml to the end of your domain and you'll probably see one already. Worth it? On a small, well linked site it barely matters. On a big site or a new one it helps google find pages quicker. It costs nothing, so submit it in Search Console and forget about it.