Celebrated, gushed over, and even legendary, something that's renowned is really famous. If you not only find a cure for cancer, but you also go on lots of talk shows so everyone knows who you are, then you'll be a renowned scientist.
Renown comes from the Anglo-Norman for "re-name," as in repeatedly name, so something is renowned is something that people are talking about, or naming, over and over. If you are a huge celebrity, people from your home town might boast, "The renowned Madame X was born here." Something renowned is really good, not just famous. Just because you make the cover of a trashy tabloid magazine doesn't mean you're a renowned actress. But if you win an Oscar, you are.