これはここだけの話ですよ。

this (indicating an item near the speaker, the action of the speaker, or the current topic); this person (usu. indicating someone in one's in-group); now; here; I (me); certainly

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

here (place physically close to the speaker, place pointed by the speaker while explaining); this place; these last (followed by a duration noun and a past sentence: time period before the present time of the speaker); these next ... (followed by a duration noun and a non past sentence: time period after the present time of the speaker); the next ...

only; just; merely; simply; no more than; nothing but; alone; as (e.g. as soon as, as much as); worth

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

talk; speech; chat; story; conversation; discussions; negotiation; argument

be; is

indicates certainty, emphasis, contempt, request, etc.; used when calling out to someone; used to catch one's breath or get someone's attention; yo!