Internet marketing, also referred to as i-marketing, web-marketing, online-marketing, Search Engine Marketing (SEM) or e-Marketing, is the marketing of products or services over the Internet.

The Internet has brought media to a global audience. The interactive nature of Internet marketing in terms of providing instant response and eliciting responses, is a unique quality of the medium. Internet marketing is sometimes considered to have a broader scope because it not only refers to the Internet, e-mail, and wireless media, but it includes management of digital customer data and electronic customer relationship management (ECRM) systems.

Internet marketing ties together creative and technical aspects of the Internet, including: design, development, advertising, and sales.

Internet marketing also refers to the placement of media along many different stages of the customer engagement cycle through search engine marketing (SEM), search engine optimization (SEO), banner ads on specific websites, e-mail marketing, and Web 2.0 strategies. In 2008 The New York Times, working with comScore, published an initial estimate to quantify the user data collected by large Internet-based companies. Counting four types of interactions with company websites in addition to the hits from advertisements served from advertising networks, the authors found the potential for collecting data upward of 2,500 times on average per user per month.

Internet marketing is relatively inexpensive when compared to the ratio of cost against the reach of the target audience. Companies can reach a wide audience for a small fraction of traditional advertising budgets. The nature of the medium allows consumers to research and purchase products and services at their own convenience. Therefore, businesses have the advantage of appealing to consumers in a medium that can bring results quickly. The strategy and overall effectiveness of marketing campaigns depend on business goals and cost-volume-profit (CVP) analysis.

Internet marketers also have the advantage of measuring statistics easily and inexpensively. Nearly all aspects of an Internet marketing campaign can be traced, measured, and tested. The advertisers can use a variety of methods: pay per impression, pay per click, pay per play, or pay per action. Therefore, marketers can determine which messages or offerings are more appealing to the audience. The results of campaigns can be measured and tracked immediately because online marketing initiatives usually require users to click on an advertisement, visit a website, and perform a targeted action. Such measurement cannot be achieved through billboard advertising, where an individual will at best be interested, then decide to obtain more information at a later time..

Because exposure, response, and overall efficiency of Internet media are easier to track than traditional off-line media—through the use of web analytics for instance—Internet marketing can offer a greater sense of accountability for advertisers. Marketers and their clients are becoming aware of the need to measure the collaborative effects of marketing (i.e., how the Internet affects in-store sales) rather than siloing each advertising medium. The effects of multichannel marketing can be difficult to determine, but are an important part of ascertaining the value of media campaigns.