Internet is the largest global internetwork，connecting tens of thousand of networks worldwide and having a“culture”that focuses on research and standardization based on real-life use．Many leading-edge network technologies come from the Internet community．The most popular and widespread Internet application services include：
     1.WWW（word wide web）　2.Electronic mail　3.File Transfer Protocol（FTP）
    1）WWW（word wide web）
    WWW is a large network of Internet servers providing hypertext and other services to terminals[3] running client applications such as a browser．
     WWW enables users to search，access，and download information from a worldwide series of networked servers where information is dynamically interlinked．A Web client passes a user’s request for information to a server，usually by way of a Web browser．
    Browser is a GUI-based hypertext client application，used to access bypertext documents and other services located on innumerable remote servers throughout the WWW and Internet．
    2）Electronic mail
    There are two kinds of E-mail protocol used in the Internet．One is Simple Mail Transfer Protocol（SMTP）which accepts incoming connections and copies messages from them into the appropriate mailboxes[8]．Another is Post Office Protocol-3（POP3）which fetches E-mail from the remote mailbox and stores it on the user’s local machine to be read later．
    3）File Transfer Protocol（FTP）
    FTP is an application protocol，part of the TCP/IP protocol stack，used for transferring files between network nodes．The TCP/IP protocols include a file transfer application program that allows users to send or receive arbitrarily large files of programs or data．
    4）Telecommunication network（Telnet）
    Telnet is a standard terminal emulation protocol in the TCP/IP protocol stack．
     因特網(wǎng)是的全球互聯(lián)網(wǎng)，連接了全世界范圍內(nèi)數(shù)以萬計(jì)的網(wǎng)絡(luò)，并已從真實(shí)生活出發(fā)形成了專注于研究和標(biāo)準(zhǔn)化的“文化”，許多前沿網(wǎng)絡(luò)技術(shù)都是來自因特網(wǎng)社會(huì)。應(yīng)用最廣的因特網(wǎng)應(yīng)用服務(wù)包括如下方面。
     1.萬維網(wǎng) 　2.電子郵件 　3.文件傳送協(xié)議（FTP） 4.遠(yuǎn)程通信網(wǎng)（Telnet）
    1）萬維網(wǎng)
    萬維網(wǎng)是一種提供因特網(wǎng)服務(wù)的大型網(wǎng)絡(luò)。
    萬維網(wǎng)允許用戶從動(dòng)態(tài)鏈接信息的全球服務(wù)器系列中搜索、訪問和下載信息，Web客戶通常通過Web瀏覽器，向服務(wù)器傳送用戶需要信息的請求。
    瀏覽器是一種基于圖形用戶界面的超文本客戶程序，通過瀏覽器可以對萬維網(wǎng)和因特網(wǎng)上無數(shù)個(gè)遠(yuǎn)程服務(wù)器上的超文本文件和其他服務(wù)進(jìn)行訪問。
    2）電子郵件
    在因特網(wǎng)上有兩種電子郵件協(xié)議，一是簡單郵件傳送協(xié)議SMTP，它接收送達(dá)的郵件并從中復(fù)制報(bào)文到相應(yīng)的郵箱，另一個(gè)郵件協(xié)議是郵局協(xié)議POP3，它從遠(yuǎn)程郵箱中取出電子郵件并將其存儲(chǔ)在用戶本地機(jī)器上，以便以后閱讀。
    3）文件傳送協(xié)議（FTP）
    FTP是TCP/IP協(xié)議棧中的應(yīng)用協(xié)議，用來在網(wǎng)絡(luò)結(jié)點(diǎn)間傳送文件。TCP/ IP協(xié)議包含一種文件傳送應(yīng)用程序，它允許用戶發(fā)送和接收任意規(guī)模的程序或數(shù)據(jù)文件。
    4）遠(yuǎn)程通信網(wǎng)（Telnet）
    它是TCP/ IP協(xié)議棧中的標(biāo)準(zhǔn)終端仿真協(xié)議。