Domain names are consist of parts separated with dots. They are:

Top-Level Domain name or TLD
Second-Level Domain name or SLD

TLD name has the last position in domain. For example, in feminaportal.com, .com is top-level domain name and feminaportal is second-level domain name. What makes your domain name unique and recognizable is SLD; in our example it is feminaportal.

Consider that www is not required part of a domain name.

TLDs are organized into several categories:

.com - commercial groups
.org - nonprofit organizations, and
.net - interactive discussion groups
.edu - educational institutions
.gov - governmental entities

Other countries have their own TLDs, for example, .rs for Serbia, .de for Germany, .ru for Russia...