Takes like three seconds to Google what it is, but essentially Elon Musk is launching 10,000 low orbit satellites to provide a truly global internet system. The distribution of satellites will allow for good internet connection worldwide, particularly in rural areas or remote areas which have long been problematic.
As far as what it does to the sky? Who the fuck cares. We've been launching our metal shit into the atmosphere for decades. What it might do for hundreds of millions of humans that suddenly have better internet access, or better alternatives to their current access? Immeasurable benefit. Countless lives made better