I work from home in my bedroom and have my desktop PC and my laptop for work. I want to run an ethernet connection from both devices into my router which is in another room.
But I don’t want to run two long separate ethernet cables into the router, I just want one long cable.
Am I supposed to use a switch for this? I mean, to plug in both the desktop PC and work laptop into the switch and have one long cable running from the switch to the router?
Yep, get a cheap unmanaged switch from Netgear, or TPLink or whoever. You’ll have one cable between switch and router, and then one cable per each device to the switch. That should do it.
I have one of the gigabit unmanaged switches from Netgear in my home office that the 3d printer, the gaming PC, and a few other things are hooked up to for that same reason.
Here’s one of the switches redocbew is referring to, https://www.amazon.com/dp/B00A128S24/. Should be about US$12-16, so shop around if you see one for more (as far as I can tell, almost all of them that look like this are identical devices, just rebranded).
I assume you have cables for the short runs? Get CAT6 or better patch cables if you don’t already have some, some nice ones are the Monoprice thin cables (high-end specs, reasonable price, look good, nice anti-snag hoods, easy to route). https://www.amazon.com/gp/product/B07958Q1Y4/