I ran into this confusion when upgrading a small office network last year. We had a switch that needed more flexibility, and the debate came up: SFP vs Ethernet module for switches. SFP is basically a compact transceiver that lets you add fiber or copper links depending on the need. An Ethernet module for switches, on the other hand, is a broader expansion option that can add multiple ports or upgrade capacity at once. In short, SFP is more about connectivity type, while modules are about scaling the whole switch. That clarity saved us from buying the wrong hardware.