If English is your native tongue like it is with mine, you know that in English "topic" and "subject" are often heavily conflated, so there isn't really a way to distinguish the two linguistically. Add to the fact that Japanese very much DOES distinguish between them explicitly, and you likely ran into issues like me when it came to は vs が.

Luckily I found a great source which gave really good explanations and examples regarding these two particles especially. However, it also covers others.

http://www.guidetojapanese.org/learn/grammar/particlesintro#The_identifier_particle