Not necessarily. Someone understands it because someone wrote the compiler. And the compiler's source (in the case of gcc) is open for review, as are the specs for things like x86, SSE, etc.
When we get to the point that computers are designing computers, the creators of the evolutionary algorithms used don't necessarily understand the output that their creations are producing.
In terms of C programmers, the programmers themselves might not understand, but they have the ability to investigate if they want to, and the compiler designers at least understand the output of their creation. When evolutionary algorithms are used to design something, we can't always grasp why the output works, we just know that it does.
When we get to the point that computers are designing computers, the creators of the evolutionary algorithms used don't necessarily understand the output that their creations are producing.
In terms of C programmers, the programmers themselves might not understand, but they have the ability to investigate if they want to, and the compiler designers at least understand the output of their creation. When evolutionary algorithms are used to design something, we can't always grasp why the output works, we just know that it does.