When a person or company uses a trademark without the owner's permission in a way that is likely to confuse or deceive the public about the source of the services and/or goods, this is known as trademark infringement.
The names of companies are crucial. They act as key marketing tools and brand statements. Even if they do not register their trademarks with the US Patent and Trademark Office, many companies, large and small, spend a lot of time and money promoting their names so that customers identify and remember them. It can be extremely aggravating to learn that another company is utilizing "your" name.
In general, trademarks do not infringe on each other if the two companies' underlying products or services do not compete and are not marketed through the same trade routes or places.
Consumer confusion is one of the primary objectives of trademark law. Allowing two bakeries with the same name and emblem to exist across the street would not be in the public interest because customers would not know which bakery's products came from. Due to customer misunderstanding, the bakery with wonderful muffins may lose business to a similarly called bakery with horrible muffins.
If, on the other hand, the two items are unrelated and unlikely to cause confusion, trademark law will not bar the two companies from utilizing the same name. To put it another way, if the same name is registered in multiple trademark classes, it does not constitute infringement.

What is Trademark Infringement?
Trademark Infringement, also called as “Trademark Violation” is defined as the prohibited usage of a licensed trademark or service, which can be related with any type of goods or services and may lead to confusion, deception, or a misunderstanding about the actual company a product or service came from. Trademark owners can take legal action if they believe their marks are being infringed. If infringement of a trademark is proven, a court order can prevent a defendant from using the mark, and the owner may be a warded monetary relief.