A content delivery network (CDN) is a large distributed system of servers deployed in multiple data centers in the Internet.^{[citation needed]} The goal of a CDN is to serve content to end-users with high availability and high performance. CDNs serve a large fraction of the Internet content today, including web objects (text, graphics, URLs and scripts), downloadable objects (media files, software, documents), applications (e-commerce, portals), live streaming media, on-demand streaming media, and social networks.

A CDN operator gets paid by content providers such as media companies and e-commerce vendors for delivering their content to their audience of end-users. In turn, a CDN pays ISPs, carriers, and network operators for hosting its servers in their data centers. Besides better performance and availability, CDNs also offload the traffic served directly from the content provider's origin infrastructure, resulting in cost savings for the content provider. In addition, CDNs provide the content provider a degree of protection from DoS attacks by using their large distributed server infrastructure to absorb the attack traffic. While most early CDNs served content using dedicated servers owned and operated by the CDN, there is a recent trend to use a hybrid model that uses P2P technology. In the hybrid model, content is served using both dedicated servers and other peer-user-owned computers as applicable.

Digital distribution (also called content delivery, online distribution, or electronic software distribution (ESD), among others) describes the delivery of media content such as audio, video, software and video games, without the use of physical media usually over online delivery mediums, such as the Internet. Digital distribution bypasses conventional physical distribution methods, such as paper or DVDs. The term online distribution is typically applied to freestanding products; downloadable add-ons for other products are more commonly known as downloadable content. An online service for distribution of application software is usually called an "application store" or "app store". With the advancement of network bandwidth capabilities, digital distribution become prominent in the 2000s.

Content distributed online may be streamed or downloaded. Streaming involves downloading and using content "on-demand" as it is needed. Meanwhile, fully downloading the content to a hard drive or other form of storage media allows for quick access in the future.