Source code refers to the code of the most original program written. The software that runs must be written, and programmers need their "language" in the process of writing programs. Musicians use staffs, architects use drawings, and the language in which programmers work is "source code".

When people usually use software, the program translates the "source code" into a form that we can intuitively express for our use.

Any website page, converted into source code, is just a bunch of words and symbols written in a certain format, but our browser helps us translate it into what we see in front of us.