A 3-tier architecture is an electronic business application system that relies on presentation, logic, and data tiers. By contrast, an n-tier architecture is an application system that relies on multiple tiers broken up into smaller subsets. N-tier architecture is based on the 3-tier architecture system, and was developed to incorporate different technologies, especially the Internet, into the existing structure.
Both 3-tier architecture and n-tier architecture are computerized business application structures that store and access data in different sections. The 3-tier system has only three such sections. It has a presentation tier, which serves as a user interface and helps translate the information from the server into something usable by clients. The logic tier coordinates different commands and performs calculations. It can move items from one tier to another. Finally, the data tier is where the files in a database are stored and retrieved.
N-tier architecture does not follow this rigid layout. It allows for flexible quantities of tiers, depending on an industry's specific needs. Some objects can even transcend the barriers of tiers. For example, many computer databases have the same security systems running at all levels of the network. The n-tier architecture is thus much more adaptable, and it allows for blurring between tiers.