What exactly does the spec “PCIe x16 slot ” mean?

What exactly does the spec “PCIe x16 slot ” mean? 4_4 slot 2 PCIe x1 slots, PCIe x2 expansion slot and interfaces with Link Aggregation Intel® Celeron® N5095 4-core4-thread processor, burst up to 4x4 mega slot 4 N : 5 dia Bots FL 42 % Channe 244 Back Pl 1 : Argle PU שש O PU 13x3x Argia 3x 3 Angle PU 10 Slot in Check Fl N ° I 127 41⁄2

4x4 mega slot 4-slot chassis with all front-accessible module slots and side-to-back airflow in a small form factor with purpose-built integrated cable management All Cisco

4040 t slot O hour slots: 4 slots O Evening slots of hours: 4 slots • LACA Slots: G-slot • Minor Slots: O 3rd year: C & P HPE Synergy 480 Gen10 Plus 4‑slot PCIe Expansion Module · QuickSpecs ·