How can a chip power up, recieve, send information with only 2 pins?
The two means I'm aware of are either have the sensor use a capacitor to store some energy, and use the same wire to send both power and signals.

In current loop systems the sensor varies its resistance to signal to the controller.  For an analogue sensor, this can just be the effect of the sensor physics, but it also can be used for digital control, allowing many devices in series connected to a single wire loop running around a factory ( my first summer job was working for Rotork's industrial control division in the '80s on such systems ).

Another shared power and signal digital mechanism is 'one wire control' where both master and slave use voltage signals. 'One wire' systems connect in parallel rather than in series, so require two wires to be run around the factory. (I suspect the name is a triumph of marketing over technical specificity).