Trademark law states that you cannot create a brand/business/organization based on a (already taken) trademark, THAT offers the same services/products, within the same geographical region.
Let me give you an example: Let's say a business selling microphones in Florida is named "soundsome". "soundsome" is their TM. Now let's say another business, also selling microphones, opens shop in Florida, with the same name (soundsome). The previous business can now sue the new business for TM infringement. But let's say, instead of selling microphones, the second business is a Recording Studio having the name "soundsome". Now, even though both businesses are based in Florida, the first business can't sue the second business (because they are selling two different types of products).
Commonness of a TM is also considered when deciding whether TM infringement has occurred. For example, "sound" will be a pretty weak TM for a company selling speakers and microphones. Why? Because the name has an intrinsic meaning. It already had a meaning before the company took it. So if another company takes-up that name, it will be harder for the first company to sue the second company because the second company can point to the intrinstic value of the TM. The best TMs are the ones that only make sense with regard to that company/brand/product/service. For example: Google, Kodak, Coca Cola, Pepsi, Nike, Adidas are amazing TMs because those names don't have any meaning outside that company/brand. Something similar happened when a software engineer in Canada named Mike Rowe, opened a website named "MikeRoweSoft". Microsoft of course sued him, but almost all legal professionals agreed that Microsoft had a pretty WEAK chance of defeating him, particularly because "Mike Rowe" was the name of the software engineer. After a few discussions (and a PR disaster for Microsoft), Microsoft reached a settlement to give that kid a FULL training in all Microsoft Products and Certifications, in return for that website (domain name). So it was a win for the kid.
Hope this helps.
