When addressing an IP network it's typical to find a few different types of use cases. It can be loopback addresses for your routers, link networks between routers, management addresses for various devices, server addresses or addresses for customers of various sorts. While the total number of addresses can easily grow into very large numbers the different use cases is often far far fewer.
Pools in NIPAP provide the possibility of grouping together prefixes for a specific use case. Assigning new addresses for that use case becomes a simple matter of getting addresses from that pool.
See CLI instructions. See Web-UI instructions.