Most routers have several 1 Gbps Ethernet ports, but some models include one or more 2.5 Gbps ports that can speed up compatible devices. A standard port is typically labeled LAN or left unlabeled and maxes out at 1 Gbps, while a 2.5G port is usually marked "2.5G" or "2.5Gb E" and may use a different color.
To benefit, both your router and your computer or other device need a 2.5 Gbps port, and you need a compatible cable. Cat5e and newer cables can handle 2.5 Gbps, but older standards will create a bottleneck. For most uses, your internet plan should also be at least 2.5 Gbps, since downloads and uploads from the internet are otherwise capped at your ISP speed. Even with slower internet, though, you can still gain from the faster link on your local network. Backing up files to a NAS can run at the full 2.5 Gbps if all devices are compatible.
The main advantage is speed. A connection 2.5 times faster than a standard port means quicker loading and downloading when moving large amounts of data. For most people, multi-gig speeds are a nice-to-have rather than a must-have, since the benefits diminish above 1 Gbps. If you regularly transfer large files or run cloud backups, however, more than doubling your speed on those devices can make a real difference.
It won't do much for everyday tasks, though. Streaming Netflix or improving online gaming performance won't noticeably change unless the rest of your network is extremely busy, because those activities don't require much bandwidth to begin with.
Source: Engadget · Summarized by HeadlinesBriefing