In the early days of the Internet, there was a mad dash to purchase domain names, and, in some cases, the owner of a brand did not purchase the .com of their brand before someone else did. When there were only a few TLDs, it made sense to also purchase the .net, .us, and .org of your brand. However, now there are just too many TLDs. I recommend only purchasing the .com. There is some interesting history to the legal dispute of a domain name in this article at nolo.com. https://www.nolo.com/legal-encyclopedia/cybersquatting-what-what-can-be-29778.html