Quick question. Im planning to finnish my second basement ever, think about possibly doing a bathroom. To the right is my sump pump. The the left is what i believe is a ejector pump. The 3 pipes from that pump, from left to right go... goes tomain sewer line, middle im not sure why its there and the far right is just my upstairs sink, not even the toilet.

Do builders just add these for drainage from the AC and a random sink, or is it there for me to be able to attach a sink/toilet/shower if i want to in the basement.

https://ibb.co/2Dpwb1L