狭义的网络广告又被称为在线广告或者互联网广告；而广义的网络广告除了包括以计算机为核心组成的计算机网络为媒介的广告行为外，还包括其他所有以电子设备相互连接而组成的网络为媒介的广告行为，例如以无线电话网络，电子信息亭网络为载体的广告行为。在一般未做特殊说明的情况下，现在各资料所谈论的网络广告全指狭义网络广告。

网络广告就是在网络上做的广告。利用网站上的广告横幅、文本链接、多媒体的方法，在互联网刊登或发布广告，通过网络传递到互联网用户的一种高科技广告运作方式。与传统的四大传播媒体（报纸、杂志、电视、广播）广告及近来备受垂青的户外广告相比，网络广告具有得天独厚的优势，是实施现代营销媒体战略的重要一部分。Internet是一个全新的广告媒体，速度最快效果很理想，是中小企业扩展装大的很好途径，对于广泛开展国际业务的公司更是如此。

Online advertising, also called online marketing or Internet advertising or web advertising, is a form of marketing and advertising which uses the Internet to deliver promotional marketing messages to consumers. It includes email marketing, search engine marketing (SEM), social media marketing, many types of display advertising (including web banner advertising), and mobile advertising. Like other advertising media, online advertising frequently involves both a publisher, who integrates advertisements into its online content, and an advertiser, who provides the advertisements to be displayed on the publisher's content. Other potential participants include advertising agencies who help generate and place the ad copy, an ad server which technologically delivers the ad and tracks statistics, and advertising affiliates who do independent promotional work for the advertiser.