A tricky one, this. Technically regarded as the first person plural, implying a collective subjectivity, its use is in fact much more complex. Indeed, the meaning can change diametrically according to context. This can be illustrated no better than with these two well-known examples of common* usage, where the collectivity implicit in the pronoun appears to be emphasised by the addition of the word 'all'. In fact, though, the meaning is rather more subtle.
A: 'We are all Thatcherites now'. Here, 'we all' refers to to 'me, my mates and Tony Blair but hardly anyone else.'
B: 'We're all in this together'. Here, by contrast, the phrase 'we all' actually refers to 'you all', that is to say everyone except me, my mates and Tony Blair, and so is generally referred to at Eton as the rhetorical second person plural.
It is, as I said, a tricky one, in the use of which only an education costing roughly the same as Mexico's national debt can really produce proficiency. Nonetheless I hope these words provide some help.
* Did I say common? You know what I mean.
[With thanks to my friend Kate for inspiration.]