Observe that $\text{C}^♯$ and $\text{D}^♭$ are the same note on the piano but are written as different notes on the staff.
This occurs with all the black keys on the piano ($\text{C}^♯$=$\text{D}^♭$, $\text{D}^♯$=$\text{E}^♭$, $\text{F}^♯$=$\text{G}^♭$, $\text{G}^♯$=$\text{A}^♭$, $\text{A}^♯$=$\text{B}^♭$). When two notes sound the same but are written as two different notes on the staff, the written notes are said to be enharmonic. Notes on the white keys of the piano can be written enharmonically as well ($\text{C}$=$\text{B}^♯$, $\text{E}$=$\text{F}^♭$, $\text{D}$=$\text{C}^𝄪$, etc.).