In computer operating systems, paging is one of the memory-management schemes by which a computer can store and retrieve data from secondary storage for use in main memory. In the paging memory-management scheme, the operating system retrieves data from secondary storage in same-size blocks called pages. The main advantage of paging over memory segmentation is that it allows the physical address space of a process to be noncontiguous. Before paging came into use, systems had to fit whole programs into storage contiguously, which caused various storage and fragmentation problems.
Paging is an important part of virtual memory implementation in most contemporary general-purpose operating systems, allowing them to use disk storage for data that does not fit into physical random-access memory (RAM).
Read more about Paging: Overview, Thrashing, Sharing, Terminology, Performance, Tuning Swap Space Size, Reliability, Addressing Limits On 32-bit Hardware