Chords are two or more notes played simultaneously that are the correct notes for a particular chord. For example, the chord of C Major uses the three notes C, E, G. That is pretty simple. If you learn the notes on the piano from left to right and obtain a piano chord book, you can play any chord and song.
Of course, the next question will be, why do people take years to learn to play the piano if it is that simple?
The answer is that they can play after a short period but how well? We learn to run at an early age, but if we wish to become an Olympic runner we have to train for years.