Those endings generally are referred to as top level domains
Internet domain names consist of parts separated by periods; the last part is the top-level domain or TLD. For example, in the domain name microsoft.com the top-level domain is com (or COM, as domain names are not case-sensitive).
Two kinds of top-level domains exist. A country code top-level domain (ccTLD) is used by a country or a dependent territory and is two letters long, for example jp for Japan). A generic top-level domain (gTLD) is three or more letters long and is used (at least in theory) by a particular class of organizations (for example, com for commercial organizations). Most gTLDs are available for use worldwide, but for historical reasons gov and mil are restricted to the government and military of the USA respectively.
Here is a list of current TLDs:
.ac Ascension Island
.ad Andorra
.ae United Arab Emirates
.aero air-transport industry
.af Afghanistan
.ag Antigua and Barbuda
.ai Anguilla
.al Albania
.am Armenia
.an Netherlands Antilles
.ao Angola
.aq Antarctica (defined here as everything south of latitude 60°S)
.ar Argentina
.arpa Address and Routing Parameter Area
.as American Samoa
.at Austria
.au Australia (including Ashmore and Cartier Islands and Coral Sea Islands)
.aw Aruba
.az Azerbaijan
.ba Bosnia and Herzegovina
.bb Barbados
.bd Bangladesh
.be Belgium
.bf Burkina Faso
.bg Bulgaria
.bh Bahrain
.bi Burundi
.biz business
.bj Benin
.bm Bermuda
.bn Brunei Darussalam
.bo Bolivia
.br Brazil
.bs Bahamas
.bt Bhutan
.bv Bouvet Island (not in use)
.bw Botswana
.by Belarus
.bz Belize
.ca Canada
.cc Cocos (Keeling) Islands
.cd Democratic Republic of the Congo (formerly Zaire)
.cf Central African Republic
.cg Republic of the Congo
.ch Switzerland (Confoederatio Helvetica)
.ci Côte d'Ivoire
.ck Cook Islands
.cl Chile
.cm Cameroon
.cn China, mainland
.co Colombia
.com commercial
.coop cooperatives
.cr Costa Rica
.cu Cuba
.cv Cape Verde
.cx Christmas Island
.cy Cyprus
.cz Czech Republic
.de Germany (Deutschland)
.dj Djibouti
.dk Denmark
.dm Dominica
.do Dominican Republic
.dz Algeria
.ec Ecuador
.edu educational (mainly U.S.)
.ee Estonia
.eg Egypt
.er Eritrea
.es Spain (España)
.et Ethiopia
.fi Finland
.fj Fiji
.fk Falkland Islands
.fm Federated States of Micronesia
.fo Faroe Islands
.fr France
.ga Gabon
.gb United Kingdom (very little used; the primary ccTLD is .uk)
.gd Grenada
.ge Georgia
.gf French Guiana
.gg Guernsey
.gh Ghana
.gi Gibraltar
.gl Greenland
.gm The Gambia
.gn Guinea
.gov United States Government
.gp Guadeloupe
.gq Equatorial Guinea
.gr Greece
.gs South Georgia and the South Sandwich Islands
.gt Guatemala
.gu Guam
.gw Guinea-Bissau
.gy Guyana
.hk Hong Kong
.hm Heard Island and McDonald Islands
.hn Honduras
.hr Croatia (Hrvatska)
.ht Haiti
.hu Hungary
.id Indonesia
.ie Ireland
.il Israel
.im Isle of Man
.in India
.info information
.int international organizations
.io British Indian Ocean Territory
.iq Iraq
.ir Iran
.is Iceland
.it Italy
.je Jersey
.jm Jamaica
.jo Jordan
.jp Japan
.ke Kenya
.kg Kyrgyzstan
.kh Cambodia
.ki Kiribati
.km Comoros
.kn Saint Kitts and Nevis
.kr South Korea
.kw Kuwait
.ky Cayman Islands
.kz Kazakhstan
.la Laos
.lb Lebanon
.lc Saint Lucia
.li Liechtenstein
.lk Sri Lanka
.lr Liberia
.ls Lesotho
.lt Lithuania
.lu Luxembourg
.lv Latvia
.ly Libya
.ma Morocco
.mc Monaco
.md Moldova
.mg Madagascar
.mh Marshall Islands
.mil United States Military
.mk Former Yugoslav Republic of Macedonia
.ml Mali
.mm Myanmar
.mn Mongolia
.mo Macau
.mp Northern Mariana Islands
.mq Martinique
.mr Mauritania
.ms Montserrat
.mt Malta
.mu Mauritius
.museum museums
.mv Maldives
.mw Malawi
.mx Mexico
.my Malaysia
.mz Mozambique
.na Namibia
.name individuals, by name
.nc New Caledonia
.ne Niger
.net network
.nf Norfolk Island
.ng Nigeria
.ni Nicaragua
.nl Netherlands
.no Norway
.np Nepal
.nr Nauru
.nu Niue
.nz New Zealand
.om Oman
.org organization
.pa Panama
.pe Peru
.pf French Polynesia (with Clipperton Island)
.pg Papua New Guinea
.ph Philippines
.pk Pakistan
.pl Poland
.pm Saint-Pierre and Miquelon
.pn Pitcairn Islands
.pr Puerto Rico
.pro professions
.ps Palestinian Territories (i.e., West Bank and Gaza Strip)
.pt Portugal
.pw Palau
.py Paraguay
.qa Qatar
.re Réunion
.ro Romania
.ru Russia
.rw Rwanda
.sa Saudi Arabia
.sb Solomon Islands
.sc Seychelles
.sd Sudan
.se Sweden
.sg Singapore
.sh Saint Helena
.si Slovenia
.sj Svalbard and Jan Mayen Islands (not in use)
.sk Slovakia
.sl Sierra Leone
.sm San Marino
.sn Senegal
.so Somalia
.sr Suriname
.st São Tomé and Príncipe
.su former Soviet Union (still in use)
.sv El Salvador
.sy Syria
.sz Swaziland
.tc Turks and Caicos Islands
.td Chad
.tf French Southern and Antarctic Lands
.tg Togo
.th Thailand
.tj Tajikistan
.tk Tokelau
.tm Turkmenistan
.tn Tunisia
.to Tonga
.tp East Timor (ISO code has changed to TL)
.tr Turkey
.tt Trinidad and Tobago
.tv Tuvalu
.tw Taiwan (Republic of China)
.tz Tanzania
.ua Ukraine
.ug Uganda
.uk United Kingdom
.um United States Minor Outlying Islands
.us United States of America
.uy Uruguay
.uz Uzbekistan
.va Vatican City State
.vc Saint Vincent and the Grenadines
.ve Venezuela
.vg British Virgin Islands
.vi U.S. Virgin Islands
.vn Vietnam
.vu Vanuatu
.wf Wallis and Futuna
.ws Samoa (formerly Western Samoa)
.ye Yemen
.yt Mayotte
.yu Yugoslavia (now Serbia and Montenegro; ISO code has changed to CS)
.za South Africa (Zuid Afrika)
.zm Zambia
.zw Zimbabwe
