Short answers, pulled from the story.
The hydraulis was the earliest known keyboard instrument created in the third century BC by an inventor in Alexandria. This pipe organ was powered by water and air and used keys balanced to require minimal force to operate.
The clavichord and harpsichord emerged during the fourteenth century to dominate the next four hundred years. The clavichord likely appeared first, followed closely by the harpsichord, and both remained common until the piano's widespread adoption in the eighteenth century.
Bartolomeo Cristofori introduced the first template for the modern piano in Italy in 1698. He named it the gravicèmbalo con piano e forte, or harpsichord with soft and loud, which allowed the pianist to control dynamics by adjusting the force with which each key was struck.
Keyboard instruments are classified based on how the performer plays the instrument rather than how the sound is produced. This classification leads to diverse families that include aerophones like the pipe organ, idiophones like the celesta, chordophones like the piano, and electrophones like synthesizers.
In historical musicology, the word keyboard refers to an instrument whose identity cannot be firmly established, particularly in the eighteenth century when the harpsichord, clavichord, and early piano competed for dominance. The term is all-inclusive and encompasses any instrument played with a keyboard regardless of its internal mechanism.