There are similarities and differences between a company name and a trademark or service mark.
Consumers don't always know the name of the company putting out a product, but if used prominently, a company name can also be a brand.
A company name usually has an LLC or Inc. in it. It is the name used to identify a business or organization and is frequently called a “trade name.” A “trademark” identifies the source of a product, and a “service mark” identifies the source of a service. Both are frequently called a “trademark” or simply a “mark.”
Merely registering a trade name with a Secretary of State’s office has been called “a trap for the unwary” because the Secretary of State only looks at other registered trade names which are identical to a proposed name. But someone else already may have trademark or service mark rights in a similar name even if it is not identical. So it is important to search for such uses or you may be limited to using your trade name solely in company listings, on contracts and in formal government documents, but not as a source designation in a trade setting.
An important difference between a trade name and a mark is that a trade name per se cannot be registered in the U.S. Patent and Trademark Office. Only if the trade name has a dual use as a trade name and also as a mark can it be regarded as registrable. So, if you use your company name on a website, it may be regarded as an unregistrable trade name if it appears in small letters at the bottom or in the URL box, but it may also function as a mark if it appears in large letters at the top of the webpage itself.
A registered mark has various advantages in pursuing an infringer. But even an unregistered trade name can be protected against the use in the same geographic area of a confusingly similar trade name or mark.
Should you use the LLC, Inc. or similar designation when the trade name also appears as a mark? That seems to be a matter of marketing preference. What counts most is how the name is used—does it refer to the company, or does it identify the source of its products or services, or both?