A top level domain name (also known as TLD) is the last part of your domain name. A few examples of TLDs are .com | .net | .eu | .uk.
Why Should I Use More than one TLD?
With more than one TLD you have a great chance to up yoar SEO. It helps people from your target countries to find your website easily via Google and other search engines, because when people search in their language, one of the things search engines look at are the TLDs of websites to determine if a website is relevant or not. For example, if someone lives in Germany, search engines are more likely to show websites with the “.de” TLD.
Nowadays there are over 500 TLDs to choose from, but the 10 first TLDs are still the most used ones for websites and the most popular ones in search engines.