Hopefully I can help. Each camera has a single Ethernet cable run to it. This both powers the camera and also transmits the video stream back. To allow the Ethernet cables to transfer power along the same line, all the cables need to feed back into a PoE switch. Here’s the one I bought which would support up to 7 cameras: https://www.amazon.com/gp/product/B00F6DL2FS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
This PoE switch then connects to your router via an Ethernet cable as well. This is what allows your home local network to now have access to the video streams from the camera. From here you have two options:
1) Connect a dedicated Network Video Recorder to the router which will “view” those video streams, record the video to an internal HD and provide additional features such as remote viewing, some notifications, etc. There are a bunch on Amazon you could look at. 2) Use your PC as the network video recorder. This is the route I went with. Instead of relying on the software on the NVR box I got to choose my software. I’m using Blue Iris ($60). This lets me fully customize the camera settings, motion alerting, notifications, etc.
I believe I can help you on this one. That's actually my company's PoE Switch. Like u/securitytech said, realistically each cam only is using 3-4Mbps. Even if you overestimated to 10Mbps per cam x8 (80 total), the 100Mbps uplink is adequate. We also do sell an 8 port ALL gigabit switch POE-SW800G that's only $10 more, however, it does not have a dedicated uplink port, but you can use any of 8 for an uplink back to the network. The downside is then you can only attach up to 7 PoE devices this way. Let me know if you have any questions.