Речь идет об употреблении it, that и this. Только прошу Вас, не надо мне говорить, что this – это «близко», а that – «далеко». Чтобы стало более ясно, приведу смущающий меня пример.

- Honey, I guess there’s something we should discuss
- Ok. What is it (this, that)?

Заранее благодарен за полноту и глубину ответов и ссылок

1. Things mentioned:

All three words can be used in the sense of “the thing or situation I have just mentioned”:

“It” does not give any special emphasis to the thing or situation.

"So she decided to paint her house pink. It upset the neighbours a bit".

"This" and "that" are more emphatic; they seem to suggest “an interesting new fact that has been mentioned”:

"So she decided to paint her house pink. This/that really upset the neighbours, as you can imagine”.

"This" seems to be preferred when the speaker has more to say about a new subject of discussion:

"So she decided to paint her house pink. This upset the neighbours so much that they took her to court, believe it or not".
"Then in 1917 he met Andrew Lewis. This was a turning point in his career: the two men entered into a partnership which lasted until…”, etc.
(More natural than “…That was a turning point…”)

2. last thing mentioned

When more than one thing has been mentioned, "it" generally refers to the main subject of discussion; "this" and "that" generally select the last thing mentioned. Compare:

"We keep the ice-cream machine in the spare room. It is mainly used by the children, incidentally". (The machine is used by the children).
"We keep the ice-cream machine in the spare room. This/that is mainly used by the children, incidentally". (The spare room is used by the children).

3. focus

"It" is only used to things, which are “in focus” – which have already been talked about. "This" can be used to “bring things into focus” before anything has been said about them. Compare:

"I enjoyed “Vampires’ Picnic”. It/this is a film for the whole family"…
"VAMPIRES’ PICNIC: THIS is a film for the whole family"
(нельзя сказать: VAMPIRES’ PICNIC: It is a film for the whole family…)

4. referring forward

Only "this" can refer forward to something that has not yet been mentioned.

"Now what do you think about this? I thought I’d get a job in Spain for six months, and then…"
(в этом случае нельзя сказать Now what do you think about it?)

Из собственного опыта, во многих речевых ситуациях "this" легче осмыслить, если добавлять в уме по-русски оборот с "вот", т.е. думать так: "вот эта вот (та самая) (штука...)" - т.е. подчеркивая бОльшую "конкретность" "this" по сравнению с "it".