The triangle is an opamp. Its output (right) is the difference of inputs (left) (plus some small offset due to manufacturing tolerances) multiplied by a large number (million or more), capped to more or less the voltage of its power rails. In most uses, there is a feedback so the output influences inputs to equalize them, effectively creating an amplifier whose voltage amplification is set by rhe strength of the feedback. Without a feedback, the opamp’s output will be either GND or Vin depending on the which input’s voltage is higher. An opamp in this configuration os known as the comparator.

The rectangle looks a bit like a European-style potentiometer but it isn’t.

Maybe two outputs because DIP-6 packages are uncommon and they went for the standard.