Understanding source code (virtual void)

[gj508]

Hello i'm a student trying to understand c++ better by looking into source code.
I have a question about one of the function used in this and other applications with multiple classes.

in Flash.h
example;
virtual void writePage(uint32_t page) = 0;
this one is called in; Flasher.cpp
on line 143 _flash->writePage(pageOffset + pageNum);

a virtual void is a void that reverance a other void with the same name and parameter from a different header.
in this project there are four;
void writePage(uint32_t page);
does this virtual void direct to all four voids or just one.

thank you in advance for reading my problem.