The twelve keys in an octave
A repeating keyboard group has twelve keys: seven white and five black. Adjacent keys are one semitone apart. The white keys are named C, D, E, F, G, A and B. From one C to the next C is an octave.
The black key immediately above C can be called C sharp (C♯). It is also one semitone below D, so it can be called D flat (D♭). These are two names for the same pitch: enharmonic equivalents. Even a white key may have another spelling: D double flat (D𝄫) sounds like C.
The full piano range
A standard piano has 88 keys, from A0 to C8. Complete twelve-key groups run from C1–B1 through C7–B7. A0–B0 and C8 are the incomplete groups at either end.
Two directions to practice
Read a note name and locate its key. Then reverse the task: look at a key and say its note name. Working in both directions makes keyboard positions easier to recall.