Can anyone provide any explanation for this hadeeth, is it referring to the one who fasts in general whether it being voluntary or during Ramadan, or is it more specific?

Question:

Is the hadith:

Narrated Sahl: The Prophet (peace be upon him) said, “There is a gate in Paradise called Ar-Raiyan, and those who observe fasts will enter through it on the Day of Resurrection and none except them will enter through it. It will be said, ‘Where are those who used to observe fasts?’ They will get up, and none except them will enter through it. After their entry the gate will be closed and nobody will enter through it.”
(Sahih al-Bukhari, Book 30, Hadith 6)

referring to the one who fasts in general whether it being voluntary or during Ramadaan, or is it more specific?

Answer:

In regards to the gate of Rayyan, then some Scholars mention that it is for those who fast the obligatory fast (Ramadan). This is the opinion of Shaikh Bin Baz rahimahullah as seen here.

Mulla Ali al-Qaari and Abul-Hasan as-Sindhi (may Allah have mercy upon them) took the view that it is those who fasted Ramadan and voluntary fasts [al-Mirqaah (6/403)]

So it is a difference of opinion.

And Allah Knows best

Faisal bin Abdul Qaadir bin Hassan
Abu Sulaymaan