Sites like zalando.de is a
list of the domains that rank on the same keywords as the current domain
in the organic (i.e. non-paid) search results or is a list of the domains
that have the a similar category as this website
How You Can
When you have a list of sites of competitors, you can
see what they do best, and you use these things on your site.
find the best site in your industry and analyze it (clicking on it)