A speaker or writer uses we to refer both to himself or herself and to one or more other people as a group. You can use we before a noun to make it clear which group of people you are referring to.
We both swore we'd be friends ever after.
我们俩人都发誓从此以后永为朋友。
We ordered another bottle of champagne.
我们又点了一瓶香槟酒。
We is sometimes used to refer to people in general.
We need to take care of our bodies.
我们需要照顾好自己的身体。
A speaker or writer may use we instead of 'I' in order to include the audience or reader in what they are saying, especially when discussing how a talk or book is organized.
We will now consider the raw materials from which the body derives energy.
我们现在来细想一下为身体提供能量的原料。