I have a danby portable air conditioner with no manual. The picture shows two ducts going outside. My question is why does the intake go outside?

On a portable a/c unit the cooling is done by taking heat out of the air inside and dispensing it outside.

That's accomplished by washing air over the heat coil in the unit, then the air goes back outside to let the heat out there.

You'll need inlet air, and outlet air to accomplish that.

Inlet air is cooler as it comes in, then that air absorbs some of the heat inside the space you're cooling and turns around to go back out leaching heat outside.

Most likely scenario.

There may be another need for outside air revolving around positive pressure inside the conditioned space.

Let me know if that doesn't solve your situ.
Russini