They are very similar but basically "Programming>General" is for general
programming questions, like "what's the best sorting algorithm for a list o strings?", while "Free Pascal>General" is for general questions about Free Pascal, like "what are the differences between ReadLn and Read?" or "how can I read a text file line by line?".
I'll admit it is thin, but there as a line separating the two concepts.
As for where you should post your question the answer is, of course: it depends on which kind of question and to what it relates.