Trademarks are for specific words or designs in connection with a particular product or service. For instance, your example of "Travel and Leisure" -- it's not the words themselves that are trademarked across the board but what these words are used in connection with, i.e. the types of products and/or services. So "Travel and Leisure" could have a trademark, for instance, for a magazine title in the field of travel related topics. If this is the example you're talking about, then you're talking about a famous, well-established brand.
For instance, Nike ® is famous trademark for clothing, shoes & retail services. That does NOT mean that you could open a restaurant called Nike, simply for the fact that when the general public hears the word Nike ®, they automatically assume it's the shoemaker. In essence, your restaurant could be accused of diluting Nike's ® famous trademark.
There are plenty of names that are NOT trademarked; however, the only way to really be sure is to have comprehensive research conducted. This entails searching the pending & registered Federal and State trademark files as well as the US National Common-Law files.
Lastly, words that are descriptive or generic (such as your examples) are typically NOT allowed to be registered as trademarks. The entire point of a trademark is to have exclusive rights to a name, logo, etc. within a particular industry. So, I could not open a shoe store called The Shoe Store and expect to get a trademark on it. Of course, like with all areas of law, there's going to be exceptions.
For instance, say you've been using a generic or descriptive name within your industry for at least 5 years -- you may be able to petition to the USPTO that you have created a distinctive name just through use alone.
Unfortunately, there's no black & white concrete answers when it comes to trademark law -- it's always gray!
I hope I've assisted you some with this matter!