What rights does having a trademark give me?

Under state law, if you own rights in a trademark (either common law rights or rights from registering with a state agency) and someone in the same geographical area uses a similar mark on similar goods and services, you can seek court relief to prevent them from continuing. However, if you obtain a federal registration for your trademark, you gain substantially greater rights, including the ability to protect your trademark on a nationwide basis and being able to file federal lawsuits to prevent trademark infringement.

In addition to being able to prevent confusing uses of the same or similar marks (that is, preventing trademark infringement), if your trademark is famous you can prevent others from diluting the mark (weakening it) even if they are not causing confusion.