Originally Posted by rxmom03
So, if I don't know what this means, then I probably am not doing it??
Correct. Calibre is one of a limited subset of computer programs that can be made to work directly from the instructions written by the programmers (the "source code"). For many programs (not including Calibre) the source code instructions are secret, and even when they are not, there is usually an intervening step ("compiling" the program) that changes those instructions from human readable to computer readable. Most Calibre users download, install and use a compiled version of the program (the "binary install").
The source code users also need to use some parts of the binary install. Usually those of us who use the source code directly don't have to update the binary install as the parts we use don't change very often. We just have to download the updated source code. Kovid is just warning us that we have to update both the binary install and the source code.