Definition of enharmonic
Enharmonic is an adjective who means: having the same pitch in the tempered scale but written in different notation.
Music notes, intervals, or key signatures can have their enharmonic equivalent.
in other words, enharmonic notes are notes that have the same pitch on a piano but have different note spellings.
Examples of enharmonics notes
Examples of enharmonics notes:
Examples of enharmonic Key Signatures
But a C♯ is like a D♭, no?
Perhaps you think that a C♯ is like a D♭, but it is not true! Why? Because a C♯ will always be a D♭ and will always be a D♭, all their life...
It will be totally crazy to replace a C♯ by a D♭, like in the example below:
A joke about enharmony?
What is the difference between a flutist who is playing a C♯ and another flutist who is playing a D♭? : One half step (semitone ) !