In a rental temporarily whilst building and internet is driving kids crazy so started looking into what's up with the prewired stuff in the house.

One room where we have 2 PCs has a wall point with 3 x ethernet ports but looking behind it to see where they go it has this weird splitting of 2 x cat5 cables across the 3 ports.
Hopefully someone has an idea whats going on here

I actually just want to use the 3 port wallpoint to connect wired to the router in the hallway

In the hallway cupboard where the manhole is there is also what appears to be a gateway plugged in?