Why is Наши necessary if Наш is already "our/ours"?
I just got to the plurals section and I found something that's a bit confusing.
There's one example that goes something like this
"Нет, наши офисы не здесь" / "No our offices are not here".
So my question is why does it use "наши" instead of just using "наш" when the meaning is identical?
I'm not sure this question is asked properly, but I hope you get what I mean.
Russian uses a lot of different endings to denote certain things. You'll run into different endings for not only possessive pronouns, but also for nouns, adjectives, and more.
While they can be confusing at first... there are some things that other languages have the Russian does not, so it all seems to balance out.
Not to scare you, but here's the entire list of the different Me, You (informal), He, She, We, You (formal), and They. http://www.russianforfree.com/grammar-of-russian-possessive-pronouns-cases.php
I don't recommend you memorize them in one go and Duo will slowly introduce them to you. But this will give you a big picture.
"Ours" indicates ownership by multiple people though, and there's never any different ending.
The only difference between "our" and "ours" is when they're used. If the subject comes before the usage you would use "ours", if it comes after you would use "our".
"This is our house"
"This house is ours".
They can also be used in situations where the subject isn't mentioned at all, but is instead very heavily implied, or common sense.
For example, if you're showing your friend something that is owned by you, and another person in a conversation, you can say
"This is ours" and it will imply that it is owned by both you, and another person whom you both know.