把域(yu)名(ming)(ming)(ming)翻譯成IP地址的(de)(de)軟件稱為域(yu)名(ming)(ming)(ming)系統，即DNS。它是(shi)(shi)一(yi)(yi)(yi)(yi)種管理名(ming)(ming)(ming)字(zi)的(de)(de)方法(fa)。這種方法(fa)是(shi)(shi)：分(fen)不同(tong)的(de)(de)組來負責(ze)各子(zi)系統的(de)(de)名(ming)(ming)(ming)字(zi)。系統中的(de)(de)每一(yi)(yi)(yi)(yi)層(ceng)(ceng)叫(jiao)做一(yi)(yi)(yi)(yi)個域(yu)，每個域(yu)用(yong)一(yi)(yi)(yi)(yi)個點分(fen)開。所謂域(yu)名(ming)(ming)(ming)服務器(qi)（即Domain Name Server，簡稱Name Server）實(shi)(shi)際上就是(shi)(shi)裝有(you)域(yu)名(ming)(ming)(ming)系統的(de)(de)主機。它是(shi)(shi)一(yi)(yi)(yi)(yi)種能夠實(shi)(shi)現名(ming)(ming)(ming)字(zi)解析（name resolution）的(de)(de)分(fen)層(ceng)(ceng)結構數據庫(ku)。

域(yu)名服(fu)(fu)務(wu)器也就是(shi)我們常(chang)說的DNS服(fu)(fu)務(wu)器，是(shi)用來對域(yu)名進(jin)行(xing)管理(li)的，通常(chang)由很多個DNS服(fu)(fu)務(wu)器組成節(jie)點，對域(yu)名進(jin)行(xing)解析，指(zhi)向你網站程序所放的服(fu)(fu)務(wu)器。

域(yu)名(ming)(ming)服務器的作用(yong)相當(dang)一個門衛，它包含了由這(zhe)(zhe)個域(yu)名(ming)(ming)的賬(zhang)戶密碼、管(guan)理策略等信息構成的數(shu)據庫。當(dang)一臺計算(suan)機(ji)登(deng)錄域(yu)名(ming)(ming)時(shi)，域(yu)控制器首先要鑒別這(zhe)(zhe)臺電腦是否(fou)是屬于這(zhe)(zhe)個域(yu)名(ming)(ming)的，用(yong)戶使用(yong)的登(deng)錄賬(zhang)號和密碼是否(fou)正確。

域(yu)(yu)(yu)(yu)名(ming)(ming)(ming)(ming)服務(wu)(wu)(wu)器(qi)(qi)(qi)是指保存(cun)有該網絡(luo)中所有主(zhu)(zhu)機的(de)(de)(de)域(yu)(yu)(yu)(yu)名(ming)(ming)(ming)(ming)和對(dui)(dui)(dui)應IP地(di)址(zhi)(zhi)，并具有將域(yu)(yu)(yu)(yu)名(ming)(ming)(ming)(ming)轉(zhuan)換為(wei)(wei)(wei)IP地(di)址(zhi)(zhi)功能的(de)(de)(de)服務(wu)(wu)(wu)器(qi)(qi)(qi)。其中 域(yu)(yu)(yu)(yu)名(ming)(ming)(ming)(ming)必須對(dui)(dui)(dui)應一(yi)個IP地(di)址(zhi)(zhi)，而(er)IP地(di)址(zhi)(zhi)不一(yi)定只(zhi)對(dui)(dui)(dui)應一(yi)個域(yu)(yu)(yu)(yu)名(ming)(ming)(ming)(ming)。域(yu)(yu)(yu)(yu)名(ming)(ming)(ming)(ming)系統采用類似目錄樹的(de)(de)(de)等級結構(gou)。域(yu)(yu)(yu)(yu)名(ming)(ming)(ming)(ming)服務(wu)(wu)(wu)器(qi)(qi)(qi)為(wei)(wei)(wei)客戶(hu)機/服務(wu)(wu)(wu)器(qi)(qi)(qi)模(mo)式中的(de)(de)(de)服務(wu)(wu)(wu)器(qi)(qi)(qi)方，它(ta)主(zhu)(zhu)要(yao)有 兩種形式：主(zhu)(zhu)服務(wu)(wu)(wu)器(qi)(qi)(qi)和轉(zhuan)發服務(wu)(wu)(wu)器(qi)(qi)(qi)。在Internet上域(yu)(yu)(yu)(yu)名(ming)(ming)(ming)(ming)與IP地(di)址(zhi)(zhi)之間(jian)(jian)是一(yi)對(dui)(dui)(dui)一(yi)（或者多對(dui)(dui)(dui)一(yi)）的(de)(de)(de)，也可采用DNS輪詢實現(xian)一(yi)對(dui)(dui)(dui)多，域(yu)(yu)(yu)(yu)名(ming)(ming)(ming)(ming)雖然便(bian)于人們記 憶，但機器(qi)(qi)(qi)之間(jian)(jian)只(zhi)認IP地(di)址(zhi)(zhi)，它(ta)們之間(jian)(jian)的(de)(de)(de)轉(zhuan)換工作稱為(wei)(wei)(wei)域(yu)(yu)(yu)(yu)名(ming)(ming)(ming)(ming)解(jie)析(xi)，域(yu)(yu)(yu)(yu)名(ming)(ming)(ming)(ming)解(jie)析(xi)需要(yao)由專(zhuan)門的(de)(de)(de)域(yu)(yu)(yu)(yu)名(ming)(ming)(ming)(ming)解(jie)析(xi)服務(wu)(wu)(wu)器(qi)(qi)(qi)來完成，DNS就是進行域(yu)(yu)(yu)(yu)名(ming)(ming)(ming)(ming)解(jie)析(xi)的(de)(de)(de)服務(wu)(wu)(wu)器(qi)(qi)(qi)。