In case you are wondering if this requires the pianist to remember the notes which the different piano chords are compiled of by heart, the answer is a definite: NO! Being familiar with a few simple basic formulas, enables one to construct required piano chords. Remembering the progression of piano chords comes spontaneously with frequent practice.

One should however avoid engaging in learning piano chords prematurely as this often results in a person learning to play only three primary chords of a specific pitched key, never to proceed beyond that point! Hence following the correct procedure in learning to play piano chords is of vital importance. 

The extend to which one first familiarizes oneself with the fundamentals, determines the extend of the success with which you will be able to play piano chords by ear.

Familiarizing oneself with the essential  fundamentals requires only a few hours of one's time, after which one can immediately start constructing and playing piano chords without anybody assisting you.