I can't seem to find a great example of when to use "его" vs "это" and was hoping somebody could shine some light on this!
For the phrase, "I remembered it", I believe it's "я помнил его" and for "It is good": "это хорошо"
Why in this instance of it is good is it not "его"?
Might it have something to do with the tenses? I can't for the life of me find an answer
Let me put it in a more systematized way. And no, it has nothing to do with tenses.
In English he refers only to male living beings, but in Russian он refers both to male living beings and also to any non-living thing which is named by a noun of the masculine gender, like стол (table), дом (house), номер (number), звук (sound), etc. In the latter case English uses it to refer to those things.
That is why:
– Ты помнишь Ивана? (Do you remember Ivan?)
– Да, я помню его. (Yes, I remember him.)
But also:
– Ты помнишь мой номер телефона? (Do you remember my phone number?)
– Да, я помню его. (Yes, I remember it.)
It is good is a different case. Actually, English has several meanings of it. Apart from referring to non-living things discussed above, English it can
1. refer to the whole situation being discussed, like:
– I've bought a new house!
– It is good!
Here it refers to the friend's buying a house, in English it can also be substituted by that ('That is good!'). In such cases both it and that are translated into Russian as это, or omitted altogether, so the dialog above is:
– Я купил новый дом!
– Это замечательно! / Замечательно!
2. introduce a new object in order to name it. Here English differentiates between singular/plural and near/far objects:
Singular: It/This/That is a lawnmower.
Plural: They/These/Those are lawnmowers.
However, Russian doesn't make any of those distinctions, and in sentences like that only это is used in most cases:
Singular: Это газонокосилка.
Plural: Это газонокосилки.
Only when you introduce a very far-away object, you can use вон то instead of это.
That is, probably, everything as for your question. Still, English has other uses of it, like in It is raining. or It was an early morning. or It was he who helped me. etc., but, when translating sentences like that into Russian, it is omitted, and neither он nor это is used:
It is raining. - Идёт дождь.
It was an early morning. - Было раннее утро.
It was he who helped me. - Именно он помог мне.
"его" means "his" or "him", "это" means "it" or "this". These are very different words.
"I remembered it" means "Я помнил это" or "Я вспомнил это" depending on the context.
"Я помнил его" would be "I remembered him"
"Это его ручка" is "It is his pen"
"Его это беспокоит" is "It bothers him"
UPDATE: @Dmitry's example is correct. The explanation is that in Russian everything has a gender, even wrenches. So, the wrench is male. That's why Russians learning English might say "I put him there" referring to a wrench, instead of correct "I put it there". It also translates into possessive forms, e.g. you'd say "Its place is there", referring to the place that belongs to a wrench. In Russian you'd say "ego mesto tam".
"его" - "him"
"I remembered it" - "Я запомнил это" (Past simple) / "Я помню (все еще) это" (Present Continuous)
