[Locksmith]

In the UK, you need to register a trademark for it to be enforceable, unlike copyright associated with literary or artistic works which accrue automatically. I don't know if the position is the same in the States, sounds like it is. So you've got to persuade someone it's worth protecting.

Essentially a trademark is designed to protect your brand investment - you could Trademark the name Star Wars and the distinctive logo if you were going to sell products under the logo, but not the characters, creatures and ideas (which are protected by copyright, even if you gave them a fancy name and logo).

So, for Sci-Fi writing and shows, it's ultimately not as important as copyright. What it allows you to stop is people selling their own products off the back of your name. For companies which make a generic product and sell a brand, like Coke or Pepsi, trademarks are their most important asset (whatever they might tell you about "secret recipes").