A trademark is a word, phrase, symbol and/or design that identifies and distinguishes the source of the goods or services of one party from those of others.
For example, here are several trademarks owned by the The Procter & Gamble Corporation:
Power Tip Bristles
A TRADE SECRET is information that companies hold in conficence to give them an advantage over their competitors. The formula for Coca-Cola is a famous trade secret. Trade secrets are protected by state laws, not by patents or trademarks.
United States patents only protect Inventions produced and sold in the United States. It is possible to protect your invention in other countries, but you must file for protection in the country where you are seeking protection.
It is important to note that even a non - U.S. patent qualifies as prior art. That means you need to search foreign patents, too.
The United States is the only country that protects the ornamental appearance of an invention with a Design Patent. Many other countries protect manufactured items with something called Industrial Designs. Here are several publications describing this type of intellectual property