In Japanese grammar, what is the difference between wa (は) and ga (が) particles?
user
Wa (は) is a topic marker and ga (が) is a subject marker. Wa (は) is used to mark something that has already been introduced to the conversation and is familiar with both the speaker and the listener. Ga (が) is used when something is newly introduced into the conversation.
assistant
Could you provide a couple of example sentences, written in Japanese with the English translation in parentheses please?
user
Here are two example sentences from the start of a fairy tale. Note how the hunter is first introduced with ga (が), and in the second sentence ga (が) is replaced with wa (は). 

昔々、狩人が住んでいました。(Once a upon a time, there lived a hunter.)
狩人は、毎朝山を登りました。(Every morning the hunter climbed up the mountain.)

N.b. unlike in these two sentences the difference is not always akin to the English distinction between "a hunter" and "the hunter".
assistant
Can you tell me a story that begins with 昔々、狩人が住んでいました
user