Web sites are found by their addresses on the World Wide Web. These addresses are known as URLs, or Uniform Resource Locators. Every website has a URL assigned to it, so both searchers and Web servers can find them quickly and easily.
Cluster analysis or clustering is the task of grouping a set of objects in such a way that objects in the same group (called a cluster) are more similar (in some sense or another) to each other than to those in other groups (clusters).
Partitioning is a general term used to describe the act of breaking up your logical data elements into multiple entities for the purpose of performance, availability, or maintainability. Sharding is the equivalent of horizontal partitioning.