What is TLD/Domain Extension?

The domain extension is the ending of a domain name, commonly referred to as TLD (Top-Level Domain).
There are many different types of TLDs, some of them are country codes, such as .uk for United Kingdom, Generic, such as .com or .org and new TLD's such as .ninja or .expert or event .london.

Some of the popular TLDs are .com, .net, .eu, .org, .biz, .me