A US Trademark is a filing with the the national registry to preserve a certain business name from use by competitors in the same line of work in the US. You can also preserve the business name usage in your state by filing the name with your Secretary of State's office (as either a corporate name or a name you are "doing business as" for a sole proprietorship).
Over the past decade I had a fantasy of making a chain of Lawlady.com branches in cities across America. I imagined little Lawlady Divorce Stores in malls everywhere, right next to Subway sandwiches and Victoria Secret.
When I learned that in Illinois there is now a Lawlady.US, this curbed my fantasy from ever having an outlet in Shumway, IL. Since Lawlady Inc is a registered Washington Corporation, the brand is protected all over Washington. I'm now limited from competing in the Illinois divorce market with Lawlady.US.
The question becomes, do I believe in the concept of little Lawlady franchises enough that I want to shell out the funds to protect my opportunity via a national Trademark registration protecting the name in other States as well.
Given that I'm still at work on a Wednesday night at 7:30 pm and feel I've got all the work I feel comfortable managing, the answer for this week is no.