Definition
IBM P Series, often written as pSeries, is older buyer language for IBM's Unix-oriented server line that commonly ran AIX workloads. Modern buying language uses IBM Power, but many installed environments and searchers still use P Series when describing AIX hardware, replacement servers, or reseller needs.
For sourcing, the important question is not the legacy name alone. Buyers should identify whether the workload runs AIX, IBM i, Linux on Power, or a mix, then map that workload to a current Power, refurbished, hosted, or maintenance option.