What is this?

[crosby1612]

I understand the "return", but what is the "cleaner" used for? There's a threaded port in the pool, I'm assuming when this valve is open, water comes through that port? But why? What attaches there and how do I use it for cleaning? And cleaning what? Sorry for all the noob questions

 

[HermanTX]

Can you show a wider shot of the equipment pad? It is unclear what other plumbing there may be.
The cleaner is a pressure side cleaner meaning it uses pump pressure to move the cleaner in the pool. Since there is no mention of a booster pump, the type cleaner required is most likely a Polaris 360 or similar model. It only uses pump pressure to move it. There would be a hose connected to the port in the pool and the cleaner would be on the end of the hose sitting on bottom of pool.
Google Polaris 360 to see how it works.

 

[crosby1612]

Ah ok. How is this different from a robotic cleaner (which we already have)? What's the need for a pressure cleaner?

 

[HermanTX]

Ah ok. How is this different from a robotic cleaner (which we already have)? What's the need for a pressure cleaner?

Pressure and Suction cleaners have been around for decades before robots became popular.
If you only wish to use a robot cleaner then just leave the cleaner valve closed or use that line as another return to the pool.